[moderation] [v9fs?] KCSAN: data-race in p9_poll_mux / p9_write_work (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 51cb1aa1250c Merge tag 'loongarch-7.2' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=105877d2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=96118c4c210877c1f9f0
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
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/4045a521ac7f/disk-51cb1aa1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e4fe4f0b82a8/vmlinux-51cb1aa1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/013e59ff6729/bzImage-51cb1aa1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+96118c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in p9_poll_mux / p9_write_work

write to 0xffff88811c6b209c of 4 bytes by task 3360 on cpu 0:
p9_write_work+0x3ff/0x710 net/9p/trans_fd.c:464
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
worker_thread+0x569/0x750 kernel/workqueue.c:3486
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88811c6b209c of 4 bytes by task 35 on cpu 1:
p9_poll_mux+0x127/0x2f0 net/9p/trans_fd.c:612
p9_poll_workfn+0xbf/0x120 net/9p/trans_fd.c:1062
process_one_work kernel/workqueue.c:3322 [inline]
process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
worker_thread+0x569/0x750 kernel/workqueue.c:3486
kthread+0x221/0x270 kernel/kthread.c:436
ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000015 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 35 Comm: kworker/1:1 Not tainted syzkaller #0 PREEMPT(lazy)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Workqueue: events p9_poll_workfn
==================================================================


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