[moderation] [net?] [bpf?] KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 23b0f90ba871 Merge tag 'sysctl-7.00-rc1' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13f3695a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=70c3ed59b49365c3
dashboard link: https://syzkaller.appspot.com/bug?extid=228054499fc5d5f26543
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [and...@kernel.org a...@kernel.org b...@vger.kernel.org dan...@iogearbox.net da...@davemloft.net edum...@google.com ho...@kernel.org ja...@cloudflare.com john.fa...@gmail.com ku...@kernel.org linux-...@vger.kernel.org net...@vger.kernel.org pab...@redhat.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ae3bcc875a04/disk-23b0f90b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1a4dbd53da8f/vmlinux-23b0f90b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3c3824777f5c/bzImage-23b0f90b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+228054...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in sk_psock_drop / unix_stream_sendmsg

write to 0xffff88810220dc08 of 8 bytes by task 3611 on cpu 1:
sk_psock_stop_verdict net/core/skmsg.c:1311 [inline]
sk_psock_drop+0x12f/0x270 net/core/skmsg.c:896
sk_psock_put include/linux/skmsg.h:506 [inline]
sock_map_unref+0x2a5/0x300 net/core/sock_map.c:185
__sock_map_delete net/core/sock_map.c:426 [inline]
sock_map_delete_from_link net/core/sock_map.c:439 [inline]
sock_map_unlink net/core/sock_map.c:1608 [inline]
sock_map_remove_links+0x228/0x340 net/core/sock_map.c:1623
sock_map_close+0xa1/0x340 net/core/sock_map.c:1684
unix_release+0x4e/0x80 net/unix/af_unix.c:1183
__sock_release net/socket.c:662 [inline]
sock_close+0x6b/0x150 net/socket.c:1455
__fput+0x29b/0x650 fs/file_table.c:469
fput_close_sync+0xad/0x190 fs/file_table.c:574
__do_sys_close fs/open.c:1509 [inline]
__se_sys_close fs/open.c:1494 [inline]
__x64_sys_close+0x55/0xf0 fs/open.c:1494
x64_sys_call+0x275d/0x3020 arch/x86/include/generated/asm/syscalls_64.h:4
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810220dc08 of 8 bytes by task 3605 on cpu 0:
unix_stream_sendmsg+0x7f8/0xbb0 net/unix/af_unix.c:2480
sock_sendmsg_nosec net/socket.c:727 [inline]
__sock_sendmsg net/socket.c:742 [inline]
____sys_sendmsg+0x5af/0x600 net/socket.c:2592
___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
__sys_sendmsg net/socket.c:2678 [inline]
__do_sys_sendmsg net/socket.c:2683 [inline]
__se_sys_sendmsg net/socket.c:2681 [inline]
__x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
x64_sys_call+0x194c/0x3020 arch/x86/include/generated/asm/syscalls_64.h:47
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff8486dd00 -> 0xffffffff8472c9f0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3605 Comm: syz.4.30 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup