[moderation] [fs?] KCSAN: data-race in pipe_poll / pipe_resize_ring (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dfd4b508c8c6 Merge tag 'drm-fixes-2025-08-16' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=177df3a2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4b9e5b4a480a9ae2
dashboard link: https://syzkaller.appspot.com/bug?extid=ae6997f4be751f834d74
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/cef435a82f61/disk-dfd4b508.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4a218551b942/vmlinux-dfd4b508.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fed0431f1d84/bzImage-dfd4b508.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ae6997...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in pipe_poll / pipe_resize_ring

write to 0xffff88811b1c8418 of 4 bytes by task 3994 on cpu 0:
pipe_resize_ring+0x2c3/0x350 fs/pipe.c:1347
pipe_set_size fs/pipe.c:1398 [inline]
pipe_fcntl+0x2e3/0x350 fs/pipe.c:1439
do_fcntl+0x667/0xdf0 fs/fcntl.c:543
__do_sys_fcntl fs/fcntl.c:591 [inline]
__se_sys_fcntl+0xb1/0x120 fs/fcntl.c:576
__x64_sys_fcntl+0x43/0x50 fs/fcntl.c:576
x64_sys_call+0x29a0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:73
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b1c8418 of 4 bytes by task 27866 on cpu 1:
pipe_poll+0x1ea/0x250 fs/pipe.c:694
vfs_poll include/linux/poll.h:82 [inline]
p9_fd_poll net/9p/trans_fd.c:240 [inline]
p9_read_work+0x715/0x8a0 net/9p/trans_fd.c:398
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
worker_thread+0x582/0x770 kernel/workqueue.c:3400
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000010 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 27866 Comm: kworker/1:8 Not tainted 6.17.0-rc1-syzkaller-00199-gdfd4b508c8c6 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: events p9_read_work
==================================================================


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[syzbot]

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