[moderation] [v9fs?] KCSAN: data-race in p9_poll_workfn / p9_write_work (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 498e47cd1d1f Fix build errors due to new UIO_MEM_DMA_COHER..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17a16421180000
kernel config: https://syzkaller.appspot.com/x/.config?x=aa27611f143168c9
dashboard link: https://syzkaller.appspot.com/bug?extid=e923f7caa88221d3ab94
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [asma...@codewreck.org eri...@kernel.org linux-...@vger.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/23aeac39659e/disk-498e47cd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/135997a3739e/vmlinux-498e47cd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/119f6deadfc6/bzImage-498e47cd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e923f7...@syzkaller.appspotmail.com

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

write to 0xffff888123b6889c of 4 bytes by task 6424 on cpu 0:
p9_write_work+0x42c/0x750 net/9p/trans_fd.c:499
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
worker_thread+0x526/0x730 kernel/workqueue.c:3416
kthread+0x1d1/0x210 kernel/kthread.c:388
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

read to 0xffff888123b6889c of 4 bytes by task 6452 on cpu 1:
p9_poll_mux net/9p/trans_fd.c:647 [inline]
p9_poll_workfn+0x2bf/0x420 net/9p/trans_fd.c:1178
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
worker_thread+0x526/0x730 kernel/workqueue.c:3416
kthread+0x1d1/0x210 kernel/kthread.c:388
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

value changed: 0x00000015 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6452 Comm: kworker/1:13 Not tainted 6.9.0-rc1-syzkaller-00011-g498e47cd1d1f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Workqueue: events p9_poll_workfn
==================================================================


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