KCSAN: data-race in p9_poll_mux / p9_write

ID	Workflow	Result	Correct	Bug	Created	Started	Finished	Revision
cb278e48	assessment-security	DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌	❓	KCSAN: data-race in p9_poll_mux / p9_write_work (2)	2026/06/28 00:00	2026/06/28 00:00	2026/06/28 00:04	fb92f11c
f6b4272a	assessment-kcsan	Benign: ✅	❓	KCSAN: data-race in p9_poll_mux / p9_write_work (2)	2026/06/26 23:48	2026/06/26 23:48	2026/06/27 00:26	7ff32d8b

Kernel	Title	Rank 🛈	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in p9_poll_mux / p9_write_work v9fs	6				1	300d	300d	0/29	auto-obsoleted due to no activity on 2025/12/24 04:28

Rank 🛈

upstream

300d

0/29

================================================================== 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 ==================================================================

Crashes (1):
Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Assets (help?)	Manager	Title
2026/06/26 23:48	upstream	51cb1aa1250c	fb92f11c	.config	console log	report			info	[disk image] [vmlinux] [kernel image]	ci2-upstream-kcsan-gce	KCSAN: data-race in p9_poll_mux / p9_write_work

Crashes (1):