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authorKuniyuki Iwashima <kuniyu@amazon.com>2023-04-08 11:49:43 -0700
committerDavid S. Miller <davem@davemloft.net>2023-04-12 10:37:00 +0100
commit9744d2bf19762703704ecba885b7ac282c02eacf (patch)
treee1c64a64b0d2355b1ca8211b7225730ab703bf8f /net/smc/af_smc.c
parent7573099e10ca69c3be33995c1fcd0d241226816d (diff)
smc: Fix use-after-free in tcp_write_timer_handler().
With Eric's ref tracker, syzbot finally found a repro for use-after-free in tcp_write_timer_handler() by kernel TCP sockets. [0] If SMC creates a kernel socket in __smc_create(), the kernel socket is supposed to be freed in smc_clcsock_release() by calling sock_release() when we close() the parent SMC socket. However, at the end of smc_clcsock_release(), the kernel socket's sk_state might not be TCP_CLOSE. This means that we have not called inet_csk_destroy_sock() in __tcp_close() and have not stopped the TCP timers. The kernel socket's TCP timers can be fired later, so we need to hold a refcnt for net as we do for MPTCP subflows in mptcp_subflow_create_socket(). [0]: leaked reference. sk_alloc (./include/net/net_namespace.h:335 net/core/sock.c:2108) inet_create (net/ipv4/af_inet.c:319 net/ipv4/af_inet.c:244) __sock_create (net/socket.c:1546) smc_create (net/smc/af_smc.c:3269 net/smc/af_smc.c:3284) __sock_create (net/socket.c:1546) __sys_socket (net/socket.c:1634 net/socket.c:1618 net/socket.c:1661) __x64_sys_socket (net/socket.c:1672) do_syscall_64 (arch/x86/entry/common.c:50 arch/x86/entry/common.c:80) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:120) ================================================================== BUG: KASAN: slab-use-after-free in tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594) Read of size 1 at addr ffff888052b65e0d by task syzrepro/18091 CPU: 0 PID: 18091 Comm: syzrepro Tainted: G W 6.3.0-rc4-01174-gb5d54eb5899a #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.amzn2022.0.1 04/01/2014 Call Trace: <IRQ> dump_stack_lvl (lib/dump_stack.c:107) print_report (mm/kasan/report.c:320 mm/kasan/report.c:430) kasan_report (mm/kasan/report.c:538) tcp_write_timer_handler (net/ipv4/tcp_timer.c:378 net/ipv4/tcp_timer.c:624 net/ipv4/tcp_timer.c:594) tcp_write_timer (./include/linux/spinlock.h:390 net/ipv4/tcp_timer.c:643) call_timer_fn (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/timer.h:127 kernel/time/timer.c:1701) __run_timers.part.0 (kernel/time/timer.c:1752 kernel/time/timer.c:2022) run_timer_softirq (kernel/time/timer.c:2037) __do_softirq (./arch/x86/include/asm/jump_label.h:27 ./include/linux/jump_label.h:207 ./include/trace/events/irq.h:142 kernel/softirq.c:572) __irq_exit_rcu (kernel/softirq.c:445 kernel/softirq.c:650) irq_exit_rcu (kernel/softirq.c:664) sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1107 (discriminator 14)) </IRQ> Fixes: ac7138746e14 ("smc: establish new socket family") Reported-by: syzbot+7e1e1bdb852961150198@syzkaller.appspotmail.com Link: https://lore.kernel.org/netdev/000000000000a3f51805f8bcc43a@google.com/ Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Reviewed-by: Tony Lu <tonylu@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/smc/af_smc.c')
-rw-r--r--net/smc/af_smc.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index c6b4a62276f6..50c38b624f77 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -3270,6 +3270,17 @@ static int __smc_create(struct net *net, struct socket *sock, int protocol,
sk_common_release(sk);
goto out;
}
+
+ /* smc_clcsock_release() does not wait smc->clcsock->sk's
+ * destruction; its sk_state might not be TCP_CLOSE after
+ * smc->sk is close()d, and TCP timers can be fired later,
+ * which need net ref.
+ */
+ sk = smc->clcsock->sk;
+ __netns_tracker_free(net, &sk->ns_tracker, false);
+ sk->sk_net_refcnt = 1;
+ get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
+ sock_inuse_add(net, 1);
} else {
smc->clcsock = clcsock;
}