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

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=87f770387a9e5dc6b79b
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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+87f770387a9e5dc6b79b@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
==================================================================


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