[moderation] [v9fs?] KCSAN: data-race in p9_poll_workfn / p9_write_work (7)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 82f2b0b97b36 Linux 6.15-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13a87670580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2de87f5e84d59a33
dashboard link: https://syzkaller.appspot.com/bug?extid=e7fe00759b8dc3c30160
compiler: Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
CC: [asma...@codewreck.org eri...@kernel.org linux-...@vger.kernel.org linu...@crudebyte.com lu...@ionkov.net v9...@lists.linux.dev]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/86d033066e86/disk-82f2b0b9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c899c05ebde6/vmlinux-82f2b0b9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1cae07effb79/bzImage-82f2b0b9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e7fe00...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in p9_poll_workfn / p9_write_work

write to 0xffff888119847c9c of 4 bytes by task 1051 on cpu 1:
p9_write_work+0x414/0x720 net/9p/trans_fd.c:500
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
worker_thread+0x582/0x770 kernel/workqueue.c:3400
kthread+0x486/0x510 kernel/kthread.c:464
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888119847c9c of 4 bytes by task 2968 on cpu 0:
p9_poll_mux net/9p/trans_fd.c:648 [inline]
p9_poll_workfn+0x1cf/0x3e0 net/9p/trans_fd.c:1172
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
worker_thread+0x582/0x770 kernel/workqueue.c:3400
kthread+0x486/0x510 kernel/kthread.c:464
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000015 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2968 Comm: kworker/0:2 Not tainted 6.15.0-rc6-syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: events p9_poll_workfn
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.