Patch "af_unix: Fix data-races around sk->sk_shutdown." has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    af_unix: Fix data-races around sk->sk_shutdown.

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     af_unix-fix-data-races-around-sk-sk_shutdown.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cb8d08ac15aa92571ced88702ae07e9f260b9190
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Fri Sep 1 17:27:07 2023 -0700

    af_unix: Fix data-races around sk->sk_shutdown.
    
    [ Upstream commit afe8764f76346ba838d4f162883e23d2fcfaa90e ]
    
    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 e1d09c2c2f57 ("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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
    Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx>
    Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/core/sock.c b/net/core/sock.c
index 4b63478cf021a..ba669f72d7df2 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2464,7 +2464,7 @@ 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;
@@ -2494,7 +2494,7 @@ 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))



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