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af_unix: Fix data-races around sk->sk_shutdown.
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[ Upstream commit afe8764 ]

sk->sk_shutdown is changed under unix_state_lock(sk), but
unix_dgram_sendmsg() calls two functions to read sk_shutdown locklessly.

  sock_alloc_send_pskb
  `- sock_wait_for_wmem

Let's use READ_ONCE() there.

Note that the writer side was marked by commit e1d09c2 ("af_unix:
Fix data races around sk->sk_shutdown.").

BUG: KCSAN: data-race in sock_alloc_send_pskb / unix_release_sock

write (marked) to 0xffff8880069af12c of 1 bytes by task 1 on cpu 1:
 unix_release_sock+0x75c/0x910 net/unix/af_unix.c:631
 unix_release+0x59/0x80 net/unix/af_unix.c:1053
 __sock_release+0x7d/0x170 net/socket.c:654
 sock_close+0x19/0x30 net/socket.c:1386
 __fput+0x2a3/0x680 fs/file_table.c:384
 ____fput+0x15/0x20 fs/file_table.c:412
 task_work_run+0x116/0x1a0 kernel/task_work.c:179
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x174/0x180 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:297
 do_syscall_64+0x4b/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

read to 0xffff8880069af12c of 1 bytes by task 28650 on cpu 0:
 sock_alloc_send_pskb+0xd2/0x620 net/core/sock.c:2767
 unix_dgram_sendmsg+0x2f8/0x14f0 net/unix/af_unix.c:1944
 unix_seqpacket_sendmsg net/unix/af_unix.c:2308 [inline]
 unix_seqpacket_sendmsg+0xba/0x130 net/unix/af_unix.c:2292
 sock_sendmsg_nosec net/socket.c:725 [inline]
 sock_sendmsg+0x148/0x160 net/socket.c:748
 ____sys_sendmsg+0x4e4/0x610 net/socket.c:2494
 ___sys_sendmsg+0xc6/0x140 net/socket.c:2548
 __sys_sendmsg+0x94/0x140 net/socket.c:2577
 __do_sys_sendmsg net/socket.c:2586 [inline]
 __se_sys_sendmsg net/socket.c:2584 [inline]
 __x64_sys_sendmsg+0x45/0x50 net/socket.c:2584
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8

value changed: 0x00 -> 0x03

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 28650 Comm: systemd-coredum Not tainted 6.4.0-11989-g6843306689af #6
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014

Fixes: 1da177e ("Linux-2.6.12-rc2")
Reported-by: syzkaller <[email protected]>
Signed-off-by: Kuniyuki Iwashima <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
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@q2ven @gregkh
q2ven authored and gregkh committed Sep 19, 2023
1 parent afc284a commit d883243
Showing 1 changed file with 2 additions and 2 deletions.
4 changes: 2 additions & 2 deletions net/core/sock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2746,7 +2746,7 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
if (refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf))
break;
if (sk->sk_shutdown & SEND_SHUTDOWN)
if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
break;
if (sk->sk_err)
break;
Expand Down Expand Up @@ -2776,7 +2776,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
goto failure;

err = -EPIPE;
if (sk->sk_shutdown & SEND_SHUTDOWN)
if (READ_ONCE(sk->sk_shutdown) & SEND_SHUTDOWN)
goto failure;

if (sk_wmem_alloc_get(sk) < READ_ONCE(sk->sk_sndbuf))
Expand Down

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