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2024-02-22Merge tag 'net-6.8.0-rc6' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net Pull networking fixes from Paolo Abeni: "Including fixes from bpf and netfilter. Current release - regressions: - af_unix: fix another unix GC hangup Previous releases - regressions: - core: fix a possible AF_UNIX deadlock - bpf: fix NULL pointer dereference in sk_psock_verdict_data_ready() - netfilter: nft_flow_offload: release dst in case direct xmit path is used - bridge: switchdev: ensure MDB events are delivered exactly once - l2tp: pass correct message length to ip6_append_data - dccp/tcp: unhash sk from ehash for tb2 alloc failure after check_estalblished() - tls: fixes for record type handling with PEEK - devlink: fix possible use-after-free and memory leaks in devlink_init() Previous releases - always broken: - bpf: fix an oops when attempting to read the vsyscall page through bpf_probe_read_kernel - sched: act_mirred: use the backlog for mirred ingress - netfilter: nft_flow_offload: fix dst refcount underflow - ipv6: sr: fix possible use-after-free and null-ptr-deref - mptcp: fix several data races - phonet: take correct lock to peek at the RX queue Misc: - handful of fixes and reliability improvements for selftests" * tag 'net-6.8.0-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (72 commits) l2tp: pass correct message length to ip6_append_data net: phy: realtek: Fix rtl8211f_config_init() for RTL8211F(D)(I)-VD-CG PHY selftests: ioam: refactoring to align with the fix Fix write to cloned skb in ipv6_hop_ioam() phonet/pep: fix racy skb_queue_empty() use phonet: take correct lock to peek at the RX queue net: sparx5: Add spinlock for frame transmission from CPU net/sched: flower: Add lock protection when remove filter handle devlink: fix port dump cmd type net: stmmac: Fix EST offset for dwmac 5.10 tools: ynl: don't leak mcast_groups on init error tools: ynl: make sure we always pass yarg to mnl_cb_run net: mctp: put sock on tag allocation failure netfilter: nf_tables: use kzalloc for hook allocation netfilter: nf_tables: register hooks last when adding new chain/flowtable netfilter: nft_flow_offload: release dst in case direct xmit path is used netfilter: nft_flow_offload: reset dst in route object after setting up flow netfilter: nf_tables: set dormant flag on hook register failure selftests: tls: add test for peeking past a record of a different type selftests: tls: add test for merging of same-type control messages ...
2024-02-22Merge tag 'trace-v6.8-rc5' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fix from Steven Rostedt: - While working on the ring buffer I noticed that the counter used for knowing where the end of the data is on a sub-buffer was not a full "int" but just 20 bits. It was masked out to 0xfffff. With the new code that allows the user to change the size of the sub-buffer, it is theoretically possible to ask for a size bigger than 2^20. If that happens, unexpected results may occur as there's no code checking if the counter overflowed the 20 bits of the write mask. There are other checks to make sure events fit in the sub-buffer, but if the sub-buffer itself is too big, that is not checked. Add a check in the resize of the sub-buffer to make sure that it never goes beyond the size of the counter that holds how much data is on it. * tag 'trace-v6.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Do not let subbuf be bigger than write mask
2024-02-22Merge tag 'for-netdev' of ↵Paolo Abeni
https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf Daniel Borkmann says: ==================== pull-request: bpf 2024-02-22 The following pull-request contains BPF updates for your *net* tree. We've added 11 non-merge commits during the last 24 day(s) which contain a total of 15 files changed, 217 insertions(+), 17 deletions(-). The main changes are: 1) Fix a syzkaller-triggered oops when attempting to read the vsyscall page through bpf_probe_read_kernel and friends, from Hou Tao. 2) Fix a kernel panic due to uninitialized iter position pointer in bpf_iter_task, from Yafang Shao. 3) Fix a race between bpf_timer_cancel_and_free and bpf_timer_cancel, from Martin KaFai Lau. 4) Fix a xsk warning in skb_add_rx_frag() (under CONFIG_DEBUG_NET) due to incorrect truesize accounting, from Sebastian Andrzej Siewior. 5) Fix a NULL pointer dereference in sk_psock_verdict_data_ready, from Shigeru Yoshida. 6) Fix a resolve_btfids warning when bpf_cpumask symbol cannot be resolved, from Hari Bathini. bpf-for-netdev * tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf: bpf, sockmap: Fix NULL pointer dereference in sk_psock_verdict_data_ready() selftests/bpf: Add negtive test cases for task iter bpf: Fix an issue due to uninitialized bpf_iter_task selftests/bpf: Test racing between bpf_timer_cancel_and_free and bpf_timer_cancel bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel selftest/bpf: Test the read of vsyscall page under x86-64 x86/mm: Disallow vsyscall page read for copy_from_kernel_nofault() x86/mm: Move is_vsyscall_vaddr() into asm/vsyscall.h bpf, scripts: Correct GPL license name xsk: Add truesize to skb_add_rx_frag(). bpf: Fix warning for bpf_cpumask in verifier ==================== Link: https://lore.kernel.org/r/20240221231826.1404-1-daniel@iogearbox.net Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2024-02-21ring-buffer: Do not let subbuf be bigger than write maskSteven Rostedt (Google)
The data on the subbuffer is measured by a write variable that also contains status flags. The counter is just 20 bits in length. If the subbuffer is bigger than then counter, it will fail. Make sure that the subbuffer can not be set to greater than the counter that keeps track of the data on the subbuffer. Link: https://lore.kernel.org/linux-trace-kernel/20240220095112.77e9cb81@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: 2808e31ec12e5 ("ring-buffer: Add interface for configuring trace sub buffer size") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-20sched/membarrier: reduce the ability to hammer on sys_membarrierLinus Torvalds
On some systems, sys_membarrier can be very expensive, causing overall slowdowns for everything. So put a lock on the path in order to serialize the accesses to prevent the ability for this to be called at too high of a frequency and saturate the machine. Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Reviewed-and-tested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Acked-by: Borislav Petkov <bp@alien8.de> Fixes: 22e4ebb97582 ("membarrier: Provide expedited private command") Fixes: c5f58bd58f43 ("membarrier: Provide GLOBAL_EXPEDITED command") Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2024-02-19bpf: Fix an issue due to uninitialized bpf_iter_taskYafang Shao
Failure to initialize it->pos, coupled with the presence of an invalid value in the flags variable, can lead to it->pos referencing an invalid task, potentially resulting in a kernel panic. To mitigate this risk, it's crucial to ensure proper initialization of it->pos to NULL. Fixes: ac8148d957f5 ("bpf: bpf_iter_task_next: use next_task(kit->task) rather than next_task(kit->pos)") Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yonghong.song@linux.dev> Acked-by: Oleg Nesterov <oleg@redhat.com> Link: https://lore.kernel.org/bpf/20240217114152.1623-2-laoar.shao@gmail.com
2024-02-19bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancelMartin KaFai Lau
The following race is possible between bpf_timer_cancel_and_free and bpf_timer_cancel. It will lead a UAF on the timer->timer. bpf_timer_cancel(); spin_lock(); t = timer->time; spin_unlock(); bpf_timer_cancel_and_free(); spin_lock(); t = timer->timer; timer->timer = NULL; spin_unlock(); hrtimer_cancel(&t->timer); kfree(t); /* UAF on t */ hrtimer_cancel(&t->timer); In bpf_timer_cancel_and_free, this patch frees the timer->timer after a rcu grace period. This requires a rcu_head addition to the "struct bpf_hrtimer". Another kfree(t) happens in bpf_timer_init, this does not need a kfree_rcu because it is still under the spin_lock and timer->timer has not been visible by others yet. In bpf_timer_cancel, rcu_read_lock() is added because this helper can be used in a non rcu critical section context (e.g. from a sleepable bpf prog). Other timer->timer usages in helpers.c have been audited, bpf_timer_cancel() is the only place where timer->timer is used outside of the spin_lock. Another solution considered is to mark a t->flag in bpf_timer_cancel and clear it after hrtimer_cancel() is done. In bpf_timer_cancel_and_free, it busy waits for the flag to be cleared before kfree(t). This patch goes with a straight forward solution and frees timer->timer after a rcu grace period. Fixes: b00628b1c7d5 ("bpf: Introduce bpf timers.") Suggested-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Hou Tao <houtao1@huawei.com> Link: https://lore.kernel.org/bpf/20240215211218.990808-1-martin.lau@linux.dev
2024-02-17Merge tag 'probes-fixes-v6.8-rc4' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull probes fix from Masami Hiramatsu: - tracing/probes: Fix BTF structure member finder to find the members which are placed after any anonymous union member correctly. * tag 'probes-fixes-v6.8-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing/probes: Fix to search structure fields correctly
2024-02-17tracing/probes: Fix to search structure fields correctlyMasami Hiramatsu (Google)
Fix to search a field from the structure which has anonymous union correctly. Since the reference `type` pointer was updated in the loop, the search loop suddenly aborted where it hits an anonymous union. Thus it can not find the field after the anonymous union. This avoids updating the cursor `type` pointer in the loop. Link: https://lore.kernel.org/all/170791694361.389532.10047514554799419688.stgit@devnote2/ Fixes: 302db0f5b3d8 ("tracing/probes: Add a function to search a member of a struct/union") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2024-02-16Merge tag 'wq-for-6.8-rc4-fixes' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq Pull workqueue fix from Tejun Heo: "Just one patch to revert commit ca10d851b9ad ("workqueue: Override implicit ordered attribute in workqueue_apply_unbound_cpumask()"). This commit could break ordering guarantees for ordered workqueues. The problem that the commit tried to resolve partially - making ordered workqueues follow unbound cpumask - is fully solved in wq/for-6.9 branch" * tag 'wq-for-6.8-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: Revert "workqueue: Override implicit ordered attribute in workqueue_apply_unbound_cpumask()"
2024-02-16Merge tag 'trace-v6.8-rc4' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix the #ifndef that didn't have the 'CONFIG_' prefix on HAVE_DYNAMIC_FTRACE_WITH_REGS The fix to have dynamic trampolines work with x86 broke arm64 as the config used in the #ifdef was HAVE_DYNAMIC_FTRACE_WITH_REGS and not CONFIG_HAVE_DYNAMIC_FTRACE_WITH_REGS which removed the fix that the previous fix was to fix. - Fix tracing_on state The code to test if "tracing_on" is set incorrectly used ring_buffer_record_is_on() which returns false if the ring buffer isn't able to be written to. But the ring buffer disable has several bits that disable it. One is internal disabling which is used for resizing and other modifications of the ring buffer. But the "tracing_on" user space visible flag should only report if tracing is actually on and not internally disabled, as this can cause confusion as writing "1" when it is disabled will not enable it. Instead use ring_buffer_record_is_set_on() which shows the user space visible settings. - Fix a false positive kmemleak on saved cmdlines Now that the saved_cmdlines structure is allocated via alloc_page() and not via kmalloc() it has become invisible to kmemleak. The allocation done to one of its pointers was flagged as a dangling allocation leak. Make kmemleak aware of this allocation and free. - Fix synthetic event dynamic strings An update that cleaned up the synthetic event code removed the return value of trace_string(), and had it return zero instead of the length, causing dynamic strings in the synthetic event to always have zero size. - Clean up documentation and header files for seq_buf * tag 'trace-v6.8-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: seq_buf: Fix kernel documentation seq_buf: Don't use "proxy" headers tracing/synthetic: Fix trace_string() return value tracing: Inform kmemleak of saved_cmdlines allocation tracing: Use ring_buffer_record_is_set_on() in tracer_tracing_is_on() tracing: Fix HAVE_DYNAMIC_FTRACE_WITH_REGS ifdef
2024-02-15tracing/synthetic: Fix trace_string() return valueThorsten Blum
Fix trace_string() by assigning the string length to the return variable which got lost in commit ddeea494a16f ("tracing/synthetic: Use union instead of casts") and caused trace_string() to always return 0. Link: https://lore.kernel.org/linux-trace-kernel/20240214220555.711598-1-thorsten.blum@toblux.com Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Fixes: ddeea494a16f ("tracing/synthetic: Use union instead of casts") Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-14tracing: Inform kmemleak of saved_cmdlines allocationSteven Rostedt (Google)
The allocation of the struct saved_cmdlines_buffer structure changed from: s = kmalloc(sizeof(*s), GFP_KERNEL); s->saved_cmdlines = kmalloc_array(TASK_COMM_LEN, val, GFP_KERNEL); to: orig_size = sizeof(*s) + val * TASK_COMM_LEN; order = get_order(orig_size); size = 1 << (order + PAGE_SHIFT); page = alloc_pages(GFP_KERNEL, order); if (!page) return NULL; s = page_address(page); memset(s, 0, sizeof(*s)); s->saved_cmdlines = kmalloc_array(TASK_COMM_LEN, val, GFP_KERNEL); Where that s->saved_cmdlines allocation looks to be a dangling allocation to kmemleak. That's because kmemleak only keeps track of kmalloc() allocations. For allocations that use page_alloc() directly, the kmemleak needs to be explicitly informed about it. Add kmemleak_alloc() and kmemleak_free() around the page allocation so that it doesn't give the following false positive: unreferenced object 0xffff8881010c8000 (size 32760): comm "swapper", pid 0, jiffies 4294667296 hex dump (first 32 bytes): ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................ ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................ backtrace (crc ae6ec1b9): [<ffffffff86722405>] kmemleak_alloc+0x45/0x80 [<ffffffff8414028d>] __kmalloc_large_node+0x10d/0x190 [<ffffffff84146ab1>] __kmalloc+0x3b1/0x4c0 [<ffffffff83ed7103>] allocate_cmdlines_buffer+0x113/0x230 [<ffffffff88649c34>] tracer_alloc_buffers.isra.0+0x124/0x460 [<ffffffff8864a174>] early_trace_init+0x14/0xa0 [<ffffffff885dd5ae>] start_kernel+0x12e/0x3c0 [<ffffffff885f5758>] x86_64_start_reservations+0x18/0x30 [<ffffffff885f582b>] x86_64_start_kernel+0x7b/0x80 [<ffffffff83a001c3>] secondary_startup_64_no_verify+0x15e/0x16b Link: https://lore.kernel.org/linux-trace-kernel/87r0hfnr9r.fsf@kernel.org/ Link: https://lore.kernel.org/linux-trace-kernel/20240214112046.09a322d6@gandalf.local.home Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Fixes: 44dc5c41b5b1 ("tracing: Fix wasted memory in saved_cmdlines logic") Reported-by: Kalle Valo <kvalo@kernel.org> Tested-by: Kalle Valo <kvalo@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-13bpf: Fix warning for bpf_cpumask in verifierHari Bathini
Compiling with CONFIG_BPF_SYSCALL & !CONFIG_BPF_JIT throws the below warning: "WARN: resolve_btfids: unresolved symbol bpf_cpumask" Fix it by adding the appropriate #ifdef. Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Jiri Olsa <jolsa@kernel.org> Acked-by: Stanislav Fomichev <sdf@google.com> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20240208100115.602172-1-hbathini@linux.ibm.com
2024-02-13tracing: Use ring_buffer_record_is_set_on() in tracer_tracing_is_on()Sven Schnelle
tracer_tracing_is_on() checks whether record_disabled is not zero. This checks both the record_disabled counter and the RB_BUFFER_OFF flag. Reading the source it looks like this function should only check for the RB_BUFFER_OFF flag. Therefore use ring_buffer_record_is_set_on(). This fixes spurious fails in the 'test for function traceon/off triggers' test from the ftrace testsuite when the system is under load. Link: https://lore.kernel.org/linux-trace-kernel/20240205065340.2848065-1-svens@linux.ibm.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Tested-By: Mete Durlu <meted@linux.ibm.com> Signed-off-by: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-13tracing: Fix HAVE_DYNAMIC_FTRACE_WITH_REGS ifdefPetr Pavlu
Commit a8b9cf62ade1 ("ftrace: Fix DIRECT_CALLS to use SAVE_REGS by default") attempted to fix an issue with direct trampolines on x86, see its description for details. However, it wrongly referenced the HAVE_DYNAMIC_FTRACE_WITH_REGS config option and the problem is still present. Add the missing "CONFIG_" prefix for the logic to work as intended. Link: https://lore.kernel.org/linux-trace-kernel/20240213132434.22537-1-petr.pavlu@suse.com Fixes: a8b9cf62ade1 ("ftrace: Fix DIRECT_CALLS to use SAVE_REGS by default") Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-11Merge tag 'timers_urgent_for_v6.8_rc4' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer fix from Borislav Petkov: - Make sure a warning is issued when a hrtimer gets queued after the timers have been migrated on the CPU down path and thus said timer will get ignored * tag 'timers_urgent_for_v6.8_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: hrtimer: Report offline hrtimer enqueue
2024-02-10Merge tag 'mm-hotfixes-stable-2024-02-10-11-16' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull misc fixes from Andrew Morton: "21 hotfixes. 12 are cc:stable and the remainder pertain to post-6.7 issues or aren't considered to be needed in earlier kernel versions" * tag 'mm-hotfixes-stable-2024-02-10-11-16' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (21 commits) nilfs2: fix potential bug in end_buffer_async_write mm/damon/sysfs-schemes: fix wrong DAMOS tried regions update timeout setup nilfs2: fix hang in nilfs_lookup_dirty_data_buffers() MAINTAINERS: Leo Yan has moved mm/zswap: don't return LRU_SKIP if we have dropped lru lock fs,hugetlb: fix NULL pointer dereference in hugetlbs_fill_super mailmap: switch email address for John Moon mm: zswap: fix objcg use-after-free in entry destruction mm/madvise: don't forget to leave lazy MMU mode in madvise_cold_or_pageout_pte_range() arch/arm/mm: fix major fault accounting when retrying under per-VMA lock selftests: core: include linux/close_range.h for CLOSE_RANGE_* macros mm/memory-failure: fix crash in split_huge_page_to_list from soft_offline_page mm: memcg: optimize parent iteration in memcg_rstat_updated() nilfs2: fix data corruption in dsync block recovery for small block sizes mm/userfaultfd: UFFDIO_MOVE implementation should use ptep_get() exit: wait_task_zombie: kill the no longer necessary spin_lock_irq(siglock) fs/proc: do_task_stat: use sig->stats_lock to gather the threads/children stats fs/proc: do_task_stat: move thread_group_cputime_adjusted() outside of lock_task_sighand() getrusage: use sig->stats_lock rather than lock_task_sighand() getrusage: move thread_group_cputime_adjusted() outside of lock_task_sighand() ...
2024-02-09Merge tag 'trace-v6.8-rc3' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix broken direct trampolines being called when another callback is attached the same function. ARM 64 does not support FTRACE_WITH_REGS, and when it added direct trampoline calls from ftrace, it removed the "WITH_REGS" flag from the ftrace_ops for direct trampolines. This broke x86 as x86 requires direct trampolines to have WITH_REGS. This wasn't noticed because direct trampolines work as long as the function it is attached to is not shared with other callbacks (like the function tracer). When there are other callbacks, a helper trampoline is called, to call all the non direct callbacks and when it returns, the direct trampoline is called. For x86, the direct trampoline sets a flag in the regs field to tell the x86 specific code to call the direct trampoline. But this only works if the ftrace_ops had WITH_REGS set. ARM does things differently that does not require this. For now, set WITH_REGS if the arch supports WITH_REGS (which ARM does not), and this makes it work for both ARM64 and x86. - Fix wasted memory in the saved_cmdlines logic. The saved_cmdlines is a cache that maps PIDs to COMMs that tracing can use. Most trace events only save the PID in the event. The saved_cmdlines file lists PIDs to COMMs so that the tracing tools can show an actual name and not just a PID for each event. There's an array of PIDs that map to a small set of saved COMM strings. The array is set to PID_MAX_DEFAULT which is usually set to 32768. When a PID comes in, it will add itself to this array along with the index into the COMM array (note if the system allows more than PID_MAX_DEFAULT, this cache is similar to cache lines as an update of a PID that has the same PID_MAX_DEFAULT bits set will flush out another task with the same matching bits set). A while ago, the size of this cache was changed to be dynamic and the array was moved into a structure and created with kmalloc(). But this new structure had the size of 131104 bytes, or 0x20020 in hex. As kmalloc allocates in powers of two, it was actually allocating 0x40000 bytes (262144) leaving 131040 bytes of wasted memory. The last element of this structure was a pointer to the COMM string array which defaulted to just saving 128 COMMs. By changing the last field of this structure to a variable length string, and just having it round up to fill the allocated memory, the default size of the saved COMM cache is now 8190. This not only uses the wasted space, but actually saves space by removing the extra allocation for the COMM names. * tag 'trace-v6.8-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracing: Fix wasted memory in saved_cmdlines logic ftrace: Fix DIRECT_CALLS to use SAVE_REGS by default
2024-02-09tracing: Fix wasted memory in saved_cmdlines logicSteven Rostedt (Google)
While looking at improving the saved_cmdlines cache I found a huge amount of wasted memory that should be used for the cmdlines. The tracing data saves pids during the trace. At sched switch, if a trace occurred, it will save the comm of the task that did the trace. This is saved in a "cache" that maps pids to comms and exposed to user space via the /sys/kernel/tracing/saved_cmdlines file. Currently it only caches by default 128 comms. The structure that uses this creates an array to store the pids using PID_MAX_DEFAULT (which is usually set to 32768). This causes the structure to be of the size of 131104 bytes on 64 bit machines. In hex: 131104 = 0x20020, and since the kernel allocates generic memory in powers of two, the kernel would allocate 0x40000 or 262144 bytes to store this structure. That leaves 131040 bytes of wasted space. Worse, the structure points to an allocated array to store the comm names, which is 16 bytes times the amount of names to save (currently 128), which is 2048 bytes. Instead of allocating a separate array, make the structure end with a variable length string and use the extra space for that. This is similar to a recommendation that Linus had made about eventfs_inode names: https://lore.kernel.org/all/20240130190355.11486-5-torvalds@linux-foundation.org/ Instead of allocating a separate string array to hold the saved comms, have the structure end with: char saved_cmdlines[]; and round up to the next power of two over sizeof(struct saved_cmdline_buffers) + num_cmdlines * TASK_COMM_LEN It will use this extra space for the saved_cmdline portion. Now, instead of saving only 128 comms by default, by using this wasted space at the end of the structure it can save over 8000 comms and even saves space by removing the need for allocating the other array. Link: https://lore.kernel.org/linux-trace-kernel/20240209063622.1f7b6d5f@rorschach.local.home Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Mete Durlu <meted@linux.ibm.com> Fixes: 939c7a4f04fcd ("tracing: Introduce saved_cmdlines_size file") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-09ftrace: Fix DIRECT_CALLS to use SAVE_REGS by defaultMasami Hiramatsu (Google)
The commit 60c8971899f3 ("ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS") changed DIRECT_CALLS to use SAVE_ARGS when there are multiple ftrace_ops at the same function, but since the x86 only support to jump to direct_call from ftrace_regs_caller, when we set the function tracer on the same target function on x86, ftrace-direct does not work as below (this actually works on arm64.) At first, insmod ftrace-direct.ko to put a direct_call on 'wake_up_process()'. # insmod kernel/samples/ftrace/ftrace-direct.ko # less trace ... <idle>-0 [006] ..s1. 564.686958: my_direct_func: waking up rcu_preempt-17 <idle>-0 [007] ..s1. 564.687836: my_direct_func: waking up kcompactd0-63 <idle>-0 [006] ..s1. 564.690926: my_direct_func: waking up rcu_preempt-17 <idle>-0 [006] ..s1. 564.696872: my_direct_func: waking up rcu_preempt-17 <idle>-0 [007] ..s1. 565.191982: my_direct_func: waking up kcompactd0-63 Setup a function filter to the 'wake_up_process' too, and enable it. # cd /sys/kernel/tracing/ # echo wake_up_process > set_ftrace_filter # echo function > current_tracer # less trace ... <idle>-0 [006] ..s3. 686.180972: wake_up_process <-call_timer_fn <idle>-0 [006] ..s3. 686.186919: wake_up_process <-call_timer_fn <idle>-0 [002] ..s3. 686.264049: wake_up_process <-call_timer_fn <idle>-0 [002] d.h6. 686.515216: wake_up_process <-kick_pool <idle>-0 [002] d.h6. 686.691386: wake_up_process <-kick_pool Then, only function tracer is shown on x86. But if you enable 'kprobe on ftrace' event (which uses SAVE_REGS flag) on the same function, it is shown again. # echo 'p wake_up_process' >> dynamic_events # echo 1 > events/kprobes/p_wake_up_process_0/enable # echo > trace # less trace ... <idle>-0 [006] ..s2. 2710.345919: p_wake_up_process_0: (wake_up_process+0x4/0x20) <idle>-0 [006] ..s3. 2710.345923: wake_up_process <-call_timer_fn <idle>-0 [006] ..s1. 2710.345928: my_direct_func: waking up rcu_preempt-17 <idle>-0 [006] ..s2. 2710.349931: p_wake_up_process_0: (wake_up_process+0x4/0x20) <idle>-0 [006] ..s3. 2710.349934: wake_up_process <-call_timer_fn <idle>-0 [006] ..s1. 2710.349937: my_direct_func: waking up rcu_preempt-17 To fix this issue, use SAVE_REGS flag for multiple ftrace_ops flag of direct_call by default. Link: https://lore.kernel.org/linux-trace-kernel/170484558617.178953.1590516949390270842.stgit@devnote2 Fixes: 60c8971899f3 ("ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS") Cc: stable@vger.kernel.org Cc: Florent Revest <revest@chromium.org> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64] Acked-by: Jiri Olsa <jolsa@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-02-08kprobes: Remove unnecessary initial values of variablesLi zeming
ri and sym is assigned first, so it does not need to initialize the assignment. Link: https://lore.kernel.org/all/20230919012823.7815-1-zeming@nfschina.com/ Signed-off-by: Li zeming <zeming@nfschina.com> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2024-02-08tracing/probes: Fix to set arg size and fmt after setting type from BTFMasami Hiramatsu (Google)
Since the BTF type setting updates probe_arg::type, the type size calculation and setting print-fmt should be done after that. Without this fix, the argument size and print-fmt can be wrong. Link: https://lore.kernel.org/all/170602218196.215583.6417859469540955777.stgit@devnote2/ Fixes: b576e09701c7 ("tracing/probes: Support function parameters if BTF is available") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2024-02-08tracing/probes: Fix to show a parse error for bad type for $commMasami Hiramatsu (Google)
Fix to show a parse error for bad type (non-string) for $comm/$COMM and immediate-string. With this fix, error_log file shows appropriate error message as below. /sys/kernel/tracing # echo 'p vfs_read $comm:u32' >> kprobe_events sh: write error: Invalid argument /sys/kernel/tracing # echo 'p vfs_read \"hoge":u32' >> kprobe_events sh: write error: Invalid argument /sys/kernel/tracing # cat error_log [ 30.144183] trace_kprobe: error: $comm and immediate-string only accepts string type Command: p vfs_read $comm:u32 ^ [ 62.618500] trace_kprobe: error: $comm and immediate-string only accepts string type Command: p vfs_read \"hoge":u32 ^ Link: https://lore.kernel.org/all/170602215411.215583.2238016352271091852.stgit@devnote2/ Fixes: 3dd1f7f24f8c ("tracing: probeevent: Fix to make the type of $comm string") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
2024-02-07exit: wait_task_zombie: kill the no longer necessary spin_lock_irq(siglock)Oleg Nesterov
After the recent changes nobody use siglock to read the values protected by stats_lock, we can kill spin_lock_irq(&current->sighand->siglock) and update the comment. With this patch only __exit_signal() and thread_group_start_cputime() take stats_lock under siglock. Link: https://lkml.kernel.org/r/20240123153359.GA21866@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Dylan Hatch <dylanbhatch@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-07getrusage: use sig->stats_lock rather than lock_task_sighand()Oleg Nesterov
lock_task_sighand() can trigger a hard lockup. If NR_CPUS threads call getrusage() at the same time and the process has NR_THREADS, spin_lock_irq will spin with irqs disabled O(NR_CPUS * NR_THREADS) time. Change getrusage() to use sig->stats_lock, it was specifically designed for this type of use. This way it runs lockless in the likely case. TODO: - Change do_task_stat() to use sig->stats_lock too, then we can remove spin_lock_irq(siglock) in wait_task_zombie(). - Turn sig->stats_lock into seqcount_rwlock_t, this way the readers in the slow mode won't exclude each other. See https://lore.kernel.org/all/20230913154907.GA26210@redhat.com/ - stats_lock has to disable irqs because ->siglock can be taken in irq context, it would be very nice to change __exit_signal() to avoid the siglock->stats_lock dependency. Link: https://lkml.kernel.org/r/20240122155053.GA26214@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Dylan Hatch <dylanbhatch@google.com> Tested-by: Dylan Hatch <dylanbhatch@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-07getrusage: move thread_group_cputime_adjusted() outside of lock_task_sighand()Oleg Nesterov
Patch series "getrusage: use sig->stats_lock", v2. This patch (of 2): thread_group_cputime() does its own locking, we can safely shift thread_group_cputime_adjusted() which does another for_each_thread loop outside of ->siglock protected section. This is also preparation for the next patch which changes getrusage() to use stats_lock instead of siglock, thread_group_cputime() takes the same lock. With the current implementation recursive read_seqbegin_or_lock() is fine, thread_group_cputime() can't enter the slow mode if the caller holds stats_lock, yet this looks more safe and better performance-wise. Link: https://lkml.kernel.org/r/20240122155023.GA26169@redhat.com Link: https://lkml.kernel.org/r/20240122155050.GA26205@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Reported-by: Dylan Hatch <dylanbhatch@google.com> Tested-by: Dylan Hatch <dylanbhatch@google.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-02-06hrtimer: Report offline hrtimer enqueueFrederic Weisbecker
The hrtimers migration on CPU-down hotplug process has been moved earlier, before the CPU actually goes to die. This leaves a small window of opportunity to queue an hrtimer in a blind spot, leaving it ignored. For example a practical case has been reported with RCU waking up a SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that way a sched/rt timer to the local offline CPU. Make sure such situations never go unnoticed and warn when that happens. Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier") Reported-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240129235646.3171983-4-boqun.feng@gmail.com
2024-02-05Revert "workqueue: Override implicit ordered attribute in ↵Tejun Heo
workqueue_apply_unbound_cpumask()" This reverts commit ca10d851b9ad0338c19e8e3089e24d565ebfffd7. The commit allowed workqueue_apply_unbound_cpumask() to clear __WQ_ORDERED on now removed implicitly ordered workqueues. This was incorrect in that system-wide config change shouldn't break ordering properties of all workqueues. The reason why apply_workqueue_attrs() path was allowed to do so was because it was targeting the specific workqueue - either the workqueue had WQ_SYSFS set or the workqueue user specifically tried to change max_active, both of which indicate that the workqueue doesn't need to be ordered. The implicitly ordered workqueue promotion was removed by the previous commit 3bc1e711c26b ("workqueue: Don't implicitly make UNBOUND workqueues w/ @max_active==1 ordered"). However, it didn't update this path and broke build. Let's revert the commit which was incorrect in the first place which also fixes build. Signed-off-by: Tejun Heo <tj@kernel.org> Fixes: 3bc1e711c26b ("workqueue: Don't implicitly make UNBOUND workqueues w/ @max_active==1 ordered") Fixes: ca10d851b9ad ("workqueue: Override implicit ordered attribute in workqueue_apply_unbound_cpumask()") Cc: stable@vger.kernel.org # v6.6+ Signed-off-by: Tejun Heo <tj@kernel.org>
2024-02-02Merge tag 'trace-v6.8-rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing and eventfs fixes from Steven Rostedt: - Fix the return code for ring_buffer_poll_wait() It was returing a -EINVAL instead of EPOLLERR. - Zero out the tracefs_inode so that all fields are initialized. The ti->private could have had stale data, but instead of just initializing it to NULL, clear out the entire structure when it is allocated. - Fix a crash in timerlat The hrtimer was initialized at read and not open, but is canceled at close. If the file was opened and never read the close will pass a NULL pointer to hrtime_cancel(). - Rewrite of eventfs. Linus wrote a patch series to remove the dentry references in the eventfs_inode and to use ref counting and more of proper VFS interfaces to make it work. - Add warning to put_ei() if ei is not set to free. That means something is about to free it when it shouldn't. - Restructure the eventfs_inode to make it more compact, and remove the unused llist field. - Remove the fsnotify*() funtions for when the inodes were being created in the lookup code. It doesn't make sense to notify about creation just because something is being looked up. - The inode hard link count was not accurate. It was being updated when a file was looked up. The inodes of directories were updating their parent inode hard link count every time the inode was created. That means if memory reclaim cleaned a stale directory inode and the inode was lookup up again, it would increment the parent inode again as well. Al Viro said to just have all eventfs directories have a hard link count of 1. That tells user space not to trust it. * tag 'trace-v6.8-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: eventfs: Keep all directory links at 1 eventfs: Remove fsnotify*() functions from lookup() eventfs: Restructure eventfs_inode structure to be more condensed eventfs: Warn if an eventfs_inode is freed without is_freed being set tracing/timerlat: Move hrtimer_init to timerlat_fd open() eventfs: Get rid of dentry pointers without refcounts eventfs: Clean up dentry ops and add revalidate function eventfs: Remove unused d_parent pointer field tracefs: dentry lookup crapectomy tracefs: Avoid using the ei->dentry pointer unnecessarily eventfs: Initialize the tracefs inode properly tracefs: Zero out the tracefs_inode when allocating it ring-buffer: Clean ring_buffer_poll_wait() error return
2024-02-01tracing/timerlat: Move hrtimer_init to timerlat_fd open()Daniel Bristot de Oliveira
Currently, the timerlat's hrtimer is initialized at the first read of timerlat_fd, and destroyed at close(). It works, but it causes an error if the user program open() and close() the file without reading. Here's an example: # echo NO_OSNOISE_WORKLOAD > /sys/kernel/debug/tracing/osnoise/options # echo timerlat > /sys/kernel/debug/tracing/current_tracer # cat <<EOF > ./timerlat_load.py # !/usr/bin/env python3 timerlat_fd = open("/sys/kernel/tracing/osnoise/per_cpu/cpu0/timerlat_fd", 'r') timerlat_fd.close(); EOF # ./taskset -c 0 ./timerlat_load.py <BOOM> BUG: kernel NULL pointer dereference, address: 0000000000000010 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI CPU: 1 PID: 2673 Comm: python3 Not tainted 6.6.13-200.fc39.x86_64 #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-1.fc39 04/01/2014 RIP: 0010:hrtimer_active+0xd/0x50 Code: 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 48 8b 57 30 <8b> 42 10 a8 01 74 09 f3 90 8b 42 10 a8 01 75 f7 80 7f 38 00 75 1d RSP: 0018:ffffb031009b7e10 EFLAGS: 00010286 RAX: 000000000002db00 RBX: ffff9118f786db08 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff9117a0e64400 RDI: ffff9118f786db08 RBP: ffff9118f786db80 R08: ffff9117a0ddd420 R09: ffff9117804d4f70 R10: 0000000000000000 R11: 0000000000000000 R12: ffff9118f786db08 R13: ffff91178fdd5e20 R14: ffff9117840978c0 R15: 0000000000000000 FS: 00007f2ffbab1740(0000) GS:ffff9118f7840000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000010 CR3: 00000001b402e000 CR4: 0000000000750ee0 PKRU: 55555554 Call Trace: <TASK> ? __die+0x23/0x70 ? page_fault_oops+0x171/0x4e0 ? srso_alias_return_thunk+0x5/0x7f ? avc_has_extended_perms+0x237/0x520 ? exc_page_fault+0x7f/0x180 ? asm_exc_page_fault+0x26/0x30 ? hrtimer_active+0xd/0x50 hrtimer_cancel+0x15/0x40 timerlat_fd_release+0x48/0xe0 __fput+0xf5/0x290 __x64_sys_close+0x3d/0x80 do_syscall_64+0x60/0x90 ? srso_alias_return_thunk+0x5/0x7f ? __x64_sys_ioctl+0x72/0xd0 ? srso_alias_return_thunk+0x5/0x7f ? syscall_exit_to_user_mode+0x2b/0x40 ? srso_alias_return_thunk+0x5/0x7f ? do_syscall_64+0x6c/0x90 ? srso_alias_return_thunk+0x5/0x7f ? exit_to_user_mode_prepare+0x142/0x1f0 ? srso_alias_return_thunk+0x5/0x7f ? syscall_exit_to_user_mode+0x2b/0x40 ? srso_alias_return_thunk+0x5/0x7f ? do_syscall_64+0x6c/0x90 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 RIP: 0033:0x7f2ffb321594 Code: 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 80 3d d5 cd 0d 00 00 74 13 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 3c c3 0f 1f 00 55 48 89 e5 48 83 ec 10 89 7d RSP: 002b:00007ffe8d8eef18 EFLAGS: 00000202 ORIG_RAX: 0000000000000003 RAX: ffffffffffffffda RBX: 00007f2ffba4e668 RCX: 00007f2ffb321594 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00007ffe8d8eef40 R08: 0000000000000000 R09: 0000000000000000 R10: 55c926e3167eae79 R11: 0000000000000202 R12: 0000000000000003 R13: 00007ffe8d8ef030 R14: 0000000000000000 R15: 00007f2ffba4e668 </TASK> CR2: 0000000000000010 ---[ end trace 0000000000000000 ]--- Move hrtimer_init to timerlat_fd open() to avoid this problem. Link: https://lore.kernel.org/linux-trace-kernel/7324dd3fc0035658c99b825204a66049389c56e3.1706798888.git.bristot@kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: stable@vger.kernel.org Fixes: e88ed227f639 ("tracing/timerlat: Add user-space interface") Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-01-31ring-buffer: Clean ring_buffer_poll_wait() error returnVincent Donnefort
The return type for ring_buffer_poll_wait() is __poll_t. This is behind the scenes an unsigned where we can set event bits. In case of a non-allocated CPU, we do return instead -EINVAL (0xffffffea). Lucky us, this ends up setting few error bits (EPOLLERR | EPOLLHUP | EPOLLNVAL), so user-space at least is aware something went wrong. Nonetheless, this is an incorrect code. Replace that -EINVAL with a proper EPOLLERR to clean that output. As this doesn't change the behaviour, there's no need to treat this change as a bug fix. Link: https://lore.kernel.org/linux-trace-kernel/20240131140955.3322792-1-vdonnefort@google.com Cc: stable@vger.kernel.org Fixes: 6721cb6002262 ("ring-buffer: Do not poll non allocated cpu buffers") Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-01-29Merge tag 'trace-v6.8-rc1-2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: "Two small fixes for tracefs and eventfs: - Fix register_snapshot_trigger() on allocation error If the snapshot fails to allocate, the register_snapshot_trigger() can still return success. If the call to tracing_alloc_snapshot_instance() returned anything but 0, it returned 0, but it should have been returning the error code from that allocation function. - Remove leftover code from tracefs doing a dentry walk on remount. The update_gid() function was called by the tracefs code on remount to update the gid of eventfs, but that is no longer the case, but that code wasn't deleted. Nothing calls it. Remove it" * tag 'trace-v6.8-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: tracefs: remove stale 'update_gid' code tracing/trigger: Fix to return error if failed to alloc snapshot
2024-01-29Merge tag 'mm-hotfixes-stable-2024-01-28-23-21' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull misc fixes from Andrew Morton: "22 hotfixes. 11 are cc:stable and the remainder address post-6.7 issues or aren't considered appropriate for backporting" * tag 'mm-hotfixes-stable-2024-01-28-23-21' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (22 commits) mm: thp_get_unmapped_area must honour topdown preference mm: huge_memory: don't force huge page alignment on 32 bit userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb selftests/mm: ksm_tests should only MADV_HUGEPAGE valid memory scs: add CONFIG_MMU dependency for vfree_atomic() mm/memory: fix folio_set_dirty() vs. folio_mark_dirty() in zap_pte_range() mm/huge_memory: fix folio_set_dirty() vs. folio_mark_dirty() selftests/mm: Update va_high_addr_switch.sh to check CPU for la57 flag selftests: mm: fix map_hugetlb failure on 64K page size systems MAINTAINERS: supplement of zswap maintainers update stackdepot: make fast paths lock-less again stackdepot: add stats counters exported via debugfs mm, kmsan: fix infinite recursion due to RCU critical section mm/writeback: fix possible divide-by-zero in wb_dirty_limits(), again selftests/mm: switch to bash from sh MAINTAINERS: add man-pages git trees mm: memcontrol: don't throttle dying tasks on memory.high mm: mmap: map MAP_STACK to VM_NOHUGEPAGE uprobes: use pagesize-aligned virtual address when replacing pages selftests/mm: mremap_test: fix build warning ...
2024-01-28Merge tag 'locking_urgent_for_v6.8_rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull locking fix from Borislav Petkov: - Prevent an inconsistent futex operation leading to stale state exposure * tag 'locking_urgent_for_v6.8_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: futex: Prevent the reuse of stale pi_state
2024-01-28Merge tag 'irq_urgent_for_v6.8_rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull irq fix from Borislav Petkov: - Initialize the resend node of each IRQ descriptor, not only the first one * tag 'irq_urgent_for_v6.8_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: genirq: Initialize resend_node hlist for all interrupt descriptors
2024-01-28Merge tag 'timers_urgent_for_v6.8_rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer fixes from Borislav Petkov: - Preserve the number of idle calls and sleep entries across CPU hotplug events in order to be able to compute correct averages - Limit the duration of the clocksource watchdog checking interval as too long intervals lead to wrongly marking the TSC as unstable * tag 'timers_urgent_for_v6.8_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: tick/sched: Preserve number of idle sleeps across CPU hotplug events clocksource: Skip watchdog check for large watchdog intervals
2024-01-26tracing/trigger: Fix to return error if failed to alloc snapshotMasami Hiramatsu (Google)
Fix register_snapshot_trigger() to return error code if it failed to allocate a snapshot instead of 0 (success). Unless that, it will register snapshot trigger without an error. Link: https://lore.kernel.org/linux-trace-kernel/170622977792.270660.2789298642759362200.stgit@devnote2 Fixes: 0bbe7f719985 ("tracing: Fix the race between registering 'snapshot' event trigger and triggering 'snapshot' operation") Cc: stable@vger.kernel.org Cc: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-01-25uprobes: use pagesize-aligned virtual address when replacing pagesDavid Hildenbrand
uprobes passes an unaligned page mapping address to folio_add_new_anon_rmap(), which ends up triggering a VM_BUG_ON() we recently extended in commit 372cbd4d5a066 ("mm: non-pmd-mappable, large folios for folio_add_new_anon_rmap()"). Arguably, this is uprobes code doing something wrong; however, for the time being it would have likely worked in rmap code because __folio_set_anon() would set folio->index to the same value. Looking at __replace_page(), we'd also pass slightly wrong values to mmu_notifier_range_init(), page_vma_mapped_walk(), flush_cache_page(), ptep_clear_flush() and set_pte_at_notify(). I suspect most of them are fine, but let's just mark the introducing commit as the one needed fixing. I don't think CC stable is warranted. We'll add more sanity checks in rmap code separately, to make sure that we always get properly aligned addresses. Link: https://lkml.kernel.org/r/20240115100731.91007-1-david@redhat.com Fixes: c517ee744b96 ("uprobes: __replace_page() should not use page_address_in_vma()") Signed-off-by: David Hildenbrand <david@redhat.com> Reported-by: Jiri Olsa <jolsa@kernel.org> Closes: https://lkml.kernel.org/r/ZaMR2EWN-HvlCfUl@krava Tested-by: Jiri Olsa <jolsa@kernel.org> Reviewed-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Alexander Shishkin Cc: Jiri Olsa <jolsa@kernel.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Ian Rogers <irogers@google.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-01-25Merge tag 'urgent-rcu.2024.01.24a' of https://github.com/neeraju/linuxLinus Torvalds
Pull RCU fix from Neeraj Upadhyay: "This fixes RCU grace period stalls, which are observed when an outgoing CPU's quiescent state reporting results in wakeup of one of the grace period kthreads, to complete the grace period. If those kthreads have SCHED_FIFO policy, the wake up can indirectly arm the RT bandwith timer to the local offline CPU. Earlier migration of the hrtimers from the CPU introduced in commit 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier") results in this timer getting ignored. If the RCU grace period kthreads are waiting for RT bandwidth to be available, they may never be actually scheduled, resulting in RCU stall warnings" * tag 'urgent-rcu.2024.01.24a' of https://github.com/neeraju/linux: rcu: Defer RCU kthreads wakeup when CPU is dying
2024-01-25tick/sched: Preserve number of idle sleeps across CPU hotplug eventsTim Chen
Commit 71fee48f ("tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplug") preserved total idle sleep time and iowait sleeptime across CPU hotplug events. Similar reasoning applies to the number of idle calls and idle sleeps to get the proper average of sleep time per idle invocation. Preserve those fields too. Fixes: 71fee48f ("tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplug") Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240122233534.3094238-1-tim.c.chen@linux.intel.com
2024-01-25clocksource: Skip watchdog check for large watchdog intervalsJiri Wiesner
There have been reports of the watchdog marking clocksources unstable on machines with 8 NUMA nodes: clocksource: timekeeping watchdog on CPU373: Marking clocksource 'tsc' as unstable because the skew is too large: clocksource: 'hpet' wd_nsec: 14523447520 clocksource: 'tsc' cs_nsec: 14524115132 The measured clocksource skew - the absolute difference between cs_nsec and wd_nsec - was 668 microseconds: cs_nsec - wd_nsec = 14524115132 - 14523447520 = 667612 The kernel used 200 microseconds for the uncertainty_margin of both the clocksource and watchdog, resulting in a threshold of 400 microseconds (the md variable). Both the cs_nsec and the wd_nsec value indicate that the readout interval was circa 14.5 seconds. The observed behaviour is that watchdog checks failed for large readout intervals on 8 NUMA node machines. This indicates that the size of the skew was directly proportinal to the length of the readout interval on those machines. The measured clocksource skew, 668 microseconds, was evaluated against a threshold (the md variable) that is suited for readout intervals of roughly WATCHDOG_INTERVAL, i.e. HZ >> 1, which is 0.5 second. The intention of 2e27e793e280 ("clocksource: Reduce clocksource-skew threshold") was to tighten the threshold for evaluating skew and set the lower bound for the uncertainty_margin of clocksources to twice WATCHDOG_MAX_SKEW. Later in c37e85c135ce ("clocksource: Loosen clocksource watchdog constraints"), the WATCHDOG_MAX_SKEW constant was increased to 125 microseconds to fit the limit of NTP, which is able to use a clocksource that suffers from up to 500 microseconds of skew per second. Both the TSC and the HPET use default uncertainty_margin. When the readout interval gets stretched the default uncertainty_margin is no longer a suitable lower bound for evaluating skew - it imposes a limit that is far stricter than the skew with which NTP can deal. The root causes of the skew being directly proportinal to the length of the readout interval are: * the inaccuracy of the shift/mult pairs of clocksources and the watchdog * the conversion to nanoseconds is imprecise for large readout intervals Prevent this by skipping the current watchdog check if the readout interval exceeds 2 * WATCHDOG_INTERVAL. Considering the maximum readout interval of 2 * WATCHDOG_INTERVAL, the current default uncertainty margin (of the TSC and HPET) corresponds to a limit on clocksource skew of 250 ppm (microseconds of skew per second). To keep the limit imposed by NTP (500 microseconds of skew per second) for all possible readout intervals, the margins would have to be scaled so that the threshold value is proportional to the length of the actual readout interval. As for why the readout interval may get stretched: Since the watchdog is executed in softirq context the expiration of the watchdog timer can get severely delayed on account of a ksoftirqd thread not getting to run in a timely manner. Surely, a system with such belated softirq execution is not working well and the scheduling issue should be looked into but the clocksource watchdog should be able to deal with it accordingly. Fixes: 2e27e793e280 ("clocksource: Reduce clocksource-skew threshold") Suggested-by: Feng Tang <feng.tang@intel.com> Signed-off-by: Jiri Wiesner <jwiesner@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Paul E. McKenney <paulmck@kernel.org> Reviewed-by: Feng Tang <feng.tang@intel.com> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240122172350.GA740@incl
2024-01-24Merge tag 'execve-v6.8-rc2' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux Pull execve fixes from Kees Cook: - Fix error handling in begin_new_exec() (Bernd Edlinger) - MAINTAINERS: specifically mention ELF (Alexey Dobriyan) - Various cleanups related to earlier open() (Askar Safin, Kees Cook) * tag 'execve-v6.8-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: exec: Distinguish in_execve from in_exec exec: Fix error handling in begin_new_exec() exec: Add do_close_execat() helper exec: remove useless comment ELF, MAINTAINERS: specifically mention ELF
2024-01-24exec: Distinguish in_execve from in_execKees Cook
Just to help distinguish the fs->in_exec flag from the current->in_execve flag, add comments in check_unsafe_exec() and copy_fs() for more context. Also note that in_execve is only used by TOMOYO now. Cc: Kentaro Takeda <takedakn@nttdata.co.jp> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: linux-fsdevel@vger.kernel.org Cc: linux-mm@kvack.org Signed-off-by: Kees Cook <keescook@chromium.org>
2024-01-24rcu: Defer RCU kthreads wakeup when CPU is dyingFrederic Weisbecker
When the CPU goes idle for the last time during the CPU down hotplug process, RCU reports a final quiescent state for the current CPU. If this quiescent state propagates up to the top, some tasks may then be woken up to complete the grace period: the main grace period kthread and/or the expedited main workqueue (or kworker). If those kthreads have a SCHED_FIFO policy, the wake up can indirectly arm the RT bandwith timer to the local offline CPU. Since this happens after hrtimers have been migrated at CPUHP_AP_HRTIMERS_DYING stage, the timer gets ignored. Therefore if the RCU kthreads are waiting for RT bandwidth to be available, they may never be actually scheduled. This triggers TREE03 rcutorture hangs: rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 4-...!: (1 GPs behind) idle=9874/1/0x4000000000000000 softirq=0/0 fqs=20 rcuc=21071 jiffies(starved) rcu: (t=21035 jiffies g=938281 q=40787 ncpus=6) rcu: rcu_preempt kthread starved for 20964 jiffies! g938281 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: task:rcu_preempt state:R running task stack:14896 pid:14 tgid:14 ppid:2 flags:0x00004000 Call Trace: <TASK> __schedule+0x2eb/0xa80 schedule+0x1f/0x90 schedule_timeout+0x163/0x270 ? __pfx_process_timeout+0x10/0x10 rcu_gp_fqs_loop+0x37c/0x5b0 ? __pfx_rcu_gp_kthread+0x10/0x10 rcu_gp_kthread+0x17c/0x200 kthread+0xde/0x110 ? __pfx_kthread+0x10/0x10 ret_from_fork+0x2b/0x40 ? __pfx_kthread+0x10/0x10 ret_from_fork_asm+0x1b/0x30 </TASK> The situation can't be solved with just unpinning the timer. The hrtimer infrastructure and the nohz heuristics involved in finding the best remote target for an unpinned timer would then also need to handle enqueues from an offline CPU in the most horrendous way. So fix this on the RCU side instead and defer the wake up to an online CPU if it's too late for the local one. Reported-by: Paul E. McKenney <paulmck@kernel.org> Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier") Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
2024-01-24genirq: Initialize resend_node hlist for all interrupt descriptorsDawei Li
For a CONFIG_SPARSE_IRQ=n kernel, early_irq_init() is supposed to initialize all interrupt descriptors. It does except for irq_desc::resend_node, which ia only initialized for the first descriptor. Use the indexed decriptor and not the base pointer to address that. Fixes: bc06a9e08742 ("genirq: Use hlist for managing resend handlers") Signed-off-by: Dawei Li <dawei.li@shingroup.cn> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Marc Zyngier <maz@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240122085716.2999875-5-dawei.li@shingroup.cn
2024-01-22tracing: Ensure visibility when inserting an element into tracing_mapPetr Pavlu
Running the following two commands in parallel on a multi-processor AArch64 machine can sporadically produce an unexpected warning about duplicate histogram entries: $ while true; do echo hist:key=id.syscall:val=hitcount > \ /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist sleep 0.001 done $ stress-ng --sysbadaddr $(nproc) The warning looks as follows: [ 2911.172474] ------------[ cut here ]------------ [ 2911.173111] Duplicates detected: 1 [ 2911.173574] WARNING: CPU: 2 PID: 12247 at kernel/trace/tracing_map.c:983 tracing_map_sort_entries+0x3e0/0x408 [ 2911.174702] Modules linked in: iscsi_ibft(E) iscsi_boot_sysfs(E) rfkill(E) af_packet(E) nls_iso8859_1(E) nls_cp437(E) vfat(E) fat(E) ena(E) tiny_power_button(E) qemu_fw_cfg(E) button(E) fuse(E) efi_pstore(E) ip_tables(E) x_tables(E) xfs(E) libcrc32c(E) aes_ce_blk(E) aes_ce_cipher(E) crct10dif_ce(E) polyval_ce(E) polyval_generic(E) ghash_ce(E) gf128mul(E) sm4_ce_gcm(E) sm4_ce_ccm(E) sm4_ce(E) sm4_ce_cipher(E) sm4(E) sm3_ce(E) sm3(E) sha3_ce(E) sha512_ce(E) sha512_arm64(E) sha2_ce(E) sha256_arm64(E) nvme(E) sha1_ce(E) nvme_core(E) nvme_auth(E) t10_pi(E) sg(E) scsi_mod(E) scsi_common(E) efivarfs(E) [ 2911.174738] Unloaded tainted modules: cppc_cpufreq(E):1 [ 2911.180985] CPU: 2 PID: 12247 Comm: cat Kdump: loaded Tainted: G E 6.7.0-default #2 1b58bbb22c97e4399dc09f92d309344f69c44a01 [ 2911.182398] Hardware name: Amazon EC2 c7g.8xlarge/, BIOS 1.0 11/1/2018 [ 2911.183208] pstate: 61400005 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) [ 2911.184038] pc : tracing_map_sort_entries+0x3e0/0x408 [ 2911.184667] lr : tracing_map_sort_entries+0x3e0/0x408 [ 2911.185310] sp : ffff8000a1513900 [ 2911.185750] x29: ffff8000a1513900 x28: ffff0003f272fe80 x27: 0000000000000001 [ 2911.186600] x26: ffff0003f272fe80 x25: 0000000000000030 x24: 0000000000000008 [ 2911.187458] x23: ffff0003c5788000 x22: ffff0003c16710c8 x21: ffff80008017f180 [ 2911.188310] x20: ffff80008017f000 x19: ffff80008017f180 x18: ffffffffffffffff [ 2911.189160] x17: 0000000000000000 x16: 0000000000000000 x15: ffff8000a15134b8 [ 2911.190015] x14: 0000000000000000 x13: 205d373432323154 x12: 5b5d313131333731 [ 2911.190844] x11: 00000000fffeffff x10: 00000000fffeffff x9 : ffffd1b78274a13c [ 2911.191716] x8 : 000000000017ffe8 x7 : c0000000fffeffff x6 : 000000000057ffa8 [ 2911.192554] x5 : ffff0012f6c24ec0 x4 : 0000000000000000 x3 : ffff2e5b72b5d000 [ 2911.193404] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0003ff254480 [ 2911.194259] Call trace: [ 2911.194626] tracing_map_sort_entries+0x3e0/0x408 [ 2911.195220] hist_show+0x124/0x800 [ 2911.195692] seq_read_iter+0x1d4/0x4e8 [ 2911.196193] seq_read+0xe8/0x138 [ 2911.196638] vfs_read+0xc8/0x300 [ 2911.197078] ksys_read+0x70/0x108 [ 2911.197534] __arm64_sys_read+0x24/0x38 [ 2911.198046] invoke_syscall+0x78/0x108 [ 2911.198553] el0_svc_common.constprop.0+0xd0/0xf8 [ 2911.199157] do_el0_svc+0x28/0x40 [ 2911.199613] el0_svc+0x40/0x178 [ 2911.200048] el0t_64_sync_handler+0x13c/0x158 [ 2911.200621] el0t_64_sync+0x1a8/0x1b0 [ 2911.201115] ---[ end trace 0000000000000000 ]--- The problem appears to be caused by CPU reordering of writes issued from __tracing_map_insert(). The check for the presence of an element with a given key in this function is: val = READ_ONCE(entry->val); if (val && keys_match(key, val->key, map->key_size)) ... The write of a new entry is: elt = get_free_elt(map); memcpy(elt->key, key, map->key_size); entry->val = elt; The "memcpy(elt->key, key, map->key_size);" and "entry->val = elt;" stores may become visible in the reversed order on another CPU. This second CPU might then incorrectly determine that a new key doesn't match an already present val->key and subsequently insert a new element, resulting in a duplicate. Fix the problem by adding a write barrier between "memcpy(elt->key, key, map->key_size);" and "entry->val = elt;", and for good measure, also use WRITE_ONCE(entry->val, elt) for publishing the element. The sequence pairs with the mentioned "READ_ONCE(entry->val);" and the "val->key" check which has an address dependency. The barrier is placed on a path executed when adding an element for a new key. Subsequent updates targeting the same key remain unaffected. From the user's perspective, the issue was introduced by commit c193707dde77 ("tracing: Remove code which merges duplicates"), which followed commit cbf4100efb8f ("tracing: Add support to detect and avoid duplicates"). The previous code operated differently; it inherently expected potential races which result in duplicates but merged them later when they occurred. Link: https://lore.kernel.org/linux-trace-kernel/20240122150928.27725-1-petr.pavlu@suse.com Fixes: c193707dde77 ("tracing: Remove code which merges duplicates") Signed-off-by: Petr Pavlu <petr.pavlu@suse.com> Acked-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-01-21Merge tag 'timers-core-2024-01-21' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer updates from Thomas Gleixner: "Updates for time and clocksources: - A fix for the idle and iowait time accounting vs CPU hotplug. The time is reset on CPU hotplug which makes the accumulated systemwide time jump backwards. - Assorted fixes and improvements for clocksource/event drivers" * tag 'timers-core-2024-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplug clocksource/drivers/ep93xx: Fix error handling during probe clocksource/drivers/cadence-ttc: Fix some kernel-doc warnings clocksource/drivers/timer-ti-dm: Fix make W=n kerneldoc warnings clocksource/timer-riscv: Add riscv_clock_shutdown callback dt-bindings: timer: Add StarFive JH8100 clint dt-bindings: timer: thead,c900-aclint-mtimer: separate mtime and mtimecmp regs
2024-01-19tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplugHeiko Carstens
When offlining and onlining CPUs the overall reported idle and iowait times as reported by /proc/stat jump backward and forward: cpu 132 0 176 225249 47 6 6 21 0 0 cpu0 80 0 115 112575 33 3 4 18 0 0 cpu1 52 0 60 112673 13 3 1 2 0 0 cpu 133 0 177 226681 47 6 6 21 0 0 cpu0 80 0 116 113387 33 3 4 18 0 0 cpu 133 0 178 114431 33 6 6 21 0 0 <---- jump backward cpu0 80 0 116 114247 33 3 4 18 0 0 cpu1 52 0 61 183 0 3 1 2 0 0 <---- idle + iowait start with 0 cpu 133 0 178 228956 47 6 6 21 0 0 <---- jump forward cpu0 81 0 117 114929 33 3 4 18 0 0 Reason for this is that get_idle_time() in fs/proc/stat.c has different sources for both values depending on if a CPU is online or offline: - if a CPU is online the values may be taken from its per cpu tick_cpu_sched structure - if a CPU is offline the values are taken from its per cpu cpustat structure The problem is that the per cpu tick_cpu_sched structure is set to zero on CPU offline. See tick_cancel_sched_timer() in kernel/time/tick-sched.c. Therefore when a CPU is brought offline and online afterwards both its idle and iowait sleeptime will be zero, causing a jump backward in total system idle and iowait sleeptime. In a similar way if a CPU is then brought offline again the total idle and iowait sleeptimes will jump forward. It looks like this behavior was introduced with commit 4b0c0f294f60 ("tick: Cleanup NOHZ per cpu data on cpu down"). This was only noticed now on s390, since we switched to generic idle time reporting with commit be76ea614460 ("s390/idle: remove arch_cpu_idle_time() and corresponding code"). Fix this by preserving the values of idle_sleeptime and iowait_sleeptime members of the per-cpu tick_sched structure on CPU hotplug. Fixes: 4b0c0f294f60 ("tick: Cleanup NOHZ per cpu data on cpu down") Reported-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20240115163555.1004144-1-hca@linux.ibm.com
2024-01-19futex: Prevent the reuse of stale pi_stateSebastian Andrzej Siewior
Jiri Slaby reported a futex state inconsistency resulting in -EINVAL during a lock operation for a PI futex. It requires that the a lock process is interrupted by a timeout or signal: T1 Owns the futex in user space. T2 Tries to acquire the futex in kernel (futex_lock_pi()). Allocates a pi_state and attaches itself to it. T2 Times out and removes its rt_waiter from the rt_mutex. Drops the rtmutex lock and tries to acquire the hash bucket lock to remove the futex_q. The lock is contended and T2 schedules out. T1 Unlocks the futex (futex_unlock_pi()). Finds a futex_q but no rt_waiter. Unlocks the futex (do_uncontended) and makes it available to user space. T3 Acquires the futex in user space. T4 Tries to acquire the futex in kernel (futex_lock_pi()). Finds the existing futex_q of T2 and tries to attach itself to the existing pi_state. This (attach_to_pi_state()) fails with -EINVAL because uval contains the TID of T3 but pi_state points to T1. It's incorrect to unlock the futex and make it available for user space to acquire as long as there is still an existing state attached to it in the kernel. T1 cannot hand over the futex to T2 because T2 already gave up and started to clean up and is blocked on the hash bucket lock, so T2's futex_q with the pi_state pointing to T1 is still queued. T2 observes the futex_q, but ignores it as there is no waiter on the corresponding rt_mutex and takes the uncontended path which allows the subsequent caller of futex_lock_pi() (T4) to observe that stale state. To prevent this the unlock path must dequeue all futex_q entries which point to the same pi_state when there is no waiter on the rt mutex. This requires obviously to make the dequeue conditional in the locking path to prevent a double dequeue. With that it's guaranteed that user space cannot observe an uncontended futex which has kernel state attached. Fixes: fbeb558b0dd0d ("futex/pi: Fix recursive rt_mutex waiter state") Reported-by: Jiri Slaby <jirislaby@kernel.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Jiri Slaby <jirislaby@kernel.org> Link: https://lore.kernel.org/r/20240118115451.0TkD_ZhB@linutronix.de Closes: https://lore.kernel.org/all/4611bcf2-44d0-4c34-9b84-17406f881003@kernel.org