From c92a7a52243871eb10e0ea2260685def47fb5094 Mon Sep 17 00:00:00 2001 From: David Vernet Date: Wed, 12 Oct 2022 18:20:14 -0500 Subject: bpf: Allow bpf_user_ringbuf_drain() callbacks to return 1 The bpf_user_ringbuf_drain() helper function allows a BPF program to specify a callback that is invoked when draining entries from a BPF_MAP_TYPE_USER_RINGBUF ring buffer map. The API is meant to allow the callback to return 0 if it wants to continue draining samples, and 1 if it's done draining. Unfortunately, bpf_user_ringbuf_drain() landed shortly after commit 1bfe26fb0827 ("bpf: Add verifier support for custom callback return range"), which changed the default behavior of callbacks to only support returning 0. This patch corrects that oversight by allowing bpf_user_ringbuf_drain() callbacks to return 0 or 1. A follow-on patch will update the user_ringbuf selftests to also return 1 from a bpf_user_ringbuf_drain() callback to prevent this from regressing in the future. Fixes: 205715673844 ("bpf: Add bpf_user_ringbuf_drain() helper") Signed-off-by: David Vernet Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20221012232015.1510043-2-void@manifault.com --- kernel/bpf/verifier.c | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/bpf/verifier.c') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6f6d2d511c06..9ab7188d8f68 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6946,6 +6946,7 @@ static int set_user_ringbuf_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } -- cgit v1.2.3 From 42378a9ca55347102bbf86708776061d8fe3ece2 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 28 Oct 2022 19:54:30 -0700 Subject: bpf, verifier: Fix memory leak in array reallocation for stack state If an error (NULL) is returned by krealloc(), callers of realloc_array() were setting their allocation pointers to NULL, but on error krealloc() does not touch the original allocation. This would result in a memory resource leak. Instead, free the old allocation on the error handling path. The memory leak information is as follows as also reported by Zhengchao: unreferenced object 0xffff888019801800 (size 256): comm "bpf_repo", pid 6490, jiffies 4294959200 (age 17.170s) hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<00000000b211474b>] __kmalloc_node_track_caller+0x45/0xc0 [<0000000086712a0b>] krealloc+0x83/0xd0 [<00000000139aab02>] realloc_array+0x82/0xe2 [<00000000b1ca41d1>] grow_stack_state+0xfb/0x186 [<00000000cd6f36d2>] check_mem_access.cold+0x141/0x1341 [<0000000081780455>] do_check_common+0x5358/0xb350 [<0000000015f6b091>] bpf_check.cold+0xc3/0x29d [<000000002973c690>] bpf_prog_load+0x13db/0x2240 [<00000000028d1644>] __sys_bpf+0x1605/0x4ce0 [<00000000053f29bd>] __x64_sys_bpf+0x75/0xb0 [<0000000056fedaf5>] do_syscall_64+0x35/0x80 [<000000002bd58261>] entry_SYSCALL_64_after_hwframe+0x63/0xcd Fixes: c69431aab67a ("bpf: verifier: Improve function state reallocation") Reported-by: Zhengchao Shao Reported-by: Kees Cook Signed-off-by: Kees Cook Signed-off-by: Daniel Borkmann Reviewed-by: Bill Wendling Cc: Lorenz Bauer Link: https://lore.kernel.org/bpf/20221029025433.2533810-1-keescook@chromium.org --- kernel/bpf/verifier.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'kernel/bpf/verifier.c') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7f0a9f6cb889..dd9019c8b0db 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1027,12 +1027,17 @@ out: */ static void *realloc_array(void *arr, size_t old_n, size_t new_n, size_t size) { + void *new_arr; + if (!new_n || old_n == new_n) goto out; - arr = krealloc_array(arr, new_n, size, GFP_KERNEL); - if (!arr) + new_arr = krealloc_array(arr, new_n, size, GFP_KERNEL); + if (!new_arr) { + kfree(arr); return NULL; + } + arr = new_arr; if (new_n > old_n) memset(arr + old_n * size, 0, (new_n - old_n) * size); -- cgit v1.2.3 From f1db20814af532f85e091231223e5e4818e8464b Mon Sep 17 00:00:00 2001 From: Youlin Li Date: Thu, 3 Nov 2022 17:34:39 +0800 Subject: bpf: Fix wrong reg type conversion in release_reference() Some helper functions will allocate memory. To avoid memory leaks, the verifier requires the eBPF program to release these memories by calling the corresponding helper functions. When a resource is released, all pointer registers corresponding to the resource should be invalidated. The verifier use release_references() to do this job, by apply __mark_reg_unknown() to each relevant register. It will give these registers the type of SCALAR_VALUE. A register that will contain a pointer value at runtime, but of type SCALAR_VALUE, which may allow the unprivileged user to get a kernel pointer by storing this register into a map. Using __mark_reg_not_init() while NOT allow_ptr_leaks can mitigate this problem. Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier") Signed-off-by: Youlin Li Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20221103093440.3161-1-liulin063@gmail.com --- kernel/bpf/verifier.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'kernel/bpf/verifier.c') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index dd9019c8b0db..225666307bba 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6623,8 +6623,12 @@ static int release_reference(struct bpf_verifier_env *env, return err; bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({ - if (reg->ref_obj_id == ref_obj_id) - __mark_reg_unknown(env, reg); + if (reg->ref_obj_id == ref_obj_id) { + if (!env->allow_ptr_leaks) + __mark_reg_not_init(env, reg); + else + __mark_reg_unknown(env, reg); + } })); return 0; -- cgit v1.2.3 From eb86559a691cea5fa63e57a03ec3dc9c31e97955 Mon Sep 17 00:00:00 2001 From: Wang Yufen Date: Tue, 8 Nov 2022 13:11:31 +0800 Subject: bpf: Fix memory leaks in __check_func_call kmemleak reports this issue: unreferenced object 0xffff88817139d000 (size 2048): comm "test_progs", pid 33246, jiffies 4307381979 (age 45851.820s) hex dump (first 32 bytes): 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [<0000000045f075f0>] kmalloc_trace+0x27/0xa0 [<0000000098b7c90a>] __check_func_call+0x316/0x1230 [<00000000b4c3c403>] check_helper_call+0x172e/0x4700 [<00000000aa3875b7>] do_check+0x21d8/0x45e0 [<000000001147357b>] do_check_common+0x767/0xaf0 [<00000000b5a595b4>] bpf_check+0x43e3/0x5bc0 [<0000000011e391b1>] bpf_prog_load+0xf26/0x1940 [<0000000007f765c0>] __sys_bpf+0xd2c/0x3650 [<00000000839815d6>] __x64_sys_bpf+0x75/0xc0 [<00000000946ee250>] do_syscall_64+0x3b/0x90 [<0000000000506b7f>] entry_SYSCALL_64_after_hwframe+0x63/0xcd The root case here is: In function prepare_func_exit(), the callee is not released in the abnormal scenario after "state->curframe--;". To fix, move "state->curframe--;" to the very bottom of the function, right when we free callee and reset frame[] pointer to NULL, as Andrii suggested. In addition, function __check_func_call() has a similar problem. In the abnormal scenario before "state->curframe++;", the callee also should be released by free_func_state(). Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier") Signed-off-by: Wang Yufen Link: https://lore.kernel.org/r/1667884291-15666-1-git-send-email-wangyufen@huawei.com Signed-off-by: Martin KaFai Lau --- kernel/bpf/verifier.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) (limited to 'kernel/bpf/verifier.c') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 225666307bba..264b3dc714cc 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6745,11 +6745,11 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn /* Transfer references to the callee */ err = copy_reference_state(callee, caller); if (err) - return err; + goto err_out; err = set_callee_state_cb(env, caller, callee, *insn_idx); if (err) - return err; + goto err_out; clear_caller_saved_regs(env, caller->regs); @@ -6766,6 +6766,11 @@ static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn print_verifier_state(env, callee, true); } return 0; + +err_out: + free_func_state(callee); + state->frame[state->curframe + 1] = NULL; + return err; } int map_set_for_each_callback_args(struct bpf_verifier_env *env, @@ -6979,8 +6984,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) return -EINVAL; } - state->curframe--; - caller = state->frame[state->curframe]; + caller = state->frame[state->curframe - 1]; if (callee->in_callback_fn) { /* enforce R0 return value range [0, 1]. */ struct tnum range = callee->callback_ret_range; @@ -7019,7 +7023,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) } /* clear everything in the callee */ free_func_state(callee); - state->frame[state->curframe + 1] = NULL; + state->frame[state->curframe--] = NULL; return 0; } -- cgit v1.2.3