KCSAN: data-race in kick_pool_pick / wq_worker_running

Status: moderation: reported on 2026/08/20 22:04
Subsystems: kernel
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+8922e6b8343f70be92e8@syzkaller.appspotmail.com
First crash: 2d09h, last: 3h18m
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
80dde489 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in kick_pool_pick / wq_worker_running 2026/08/22 00:00 2026/08/22 00:00 2026/08/22 00:14 1e72964b
c85495d2 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in kick_pool_pick / wq_worker_running 2026/08/20 22:03 2026/08/20 22:04 2026/08/20 22:27 1e72964b

Sample crash report:
==================================================================
BUG: KCSAN: data-race in kick_pool_pick / wq_worker_running

read-write to 0xffff888237c2abe4 of 4 bytes by task 3409 on cpu 0:
 wq_worker_running+0x9c/0x120 kernel/workqueue.c:1465
 synchronize_rcu_expedited+0x5f8/0x770 kernel/rcu/tree_exp.h:979
 srcu_readers_active_idx_check kernel/rcu/srcutree.c:537 [inline]
 try_check_zero+0x189/0x260 kernel/rcu/srcutree.c:1154
 srcu_advance_state kernel/rcu/srcutree.c:1846 [inline]
 process_srcu+0xc6/0xd90 kernel/rcu/srcutree.c:1973
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3470
 worker_thread+0x569/0x750 kernel/workqueue.c:3551
 kthread+0x223/0x270 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 0xffff888237c2abe4 of 4 bytes by task 3338 on cpu 1:
 need_more_worker kernel/workqueue.c:954 [inline]
 kick_pool_pick+0x5f/0x310 kernel/workqueue.c:1284
 __queue_work+0x90a/0xbc0 kernel/workqueue.c:2449
 queue_work_on+0xa9/0x140 kernel/workqueue.c:2501
 srcu_queue_delayed_work_on kernel/rcu/srcutree.c:873 [inline]
 srcu_schedule_cbs_sdp kernel/rcu/srcutree.c:886 [inline]
 srcu_gp_end kernel/rcu/srcutree.c:951 [inline]
 srcu_advance_state kernel/rcu/srcutree.c:1869 [inline]
 process_srcu+0xa39/0xd90 kernel/rcu/srcutree.c:1973
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3470
 worker_thread+0x569/0x750 kernel/workqueue.c:3551
 kthread+0x223/0x270 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: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3338 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: rcu_gp process_srcu
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/23 04:34 upstream 66fb95a52111 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in kick_pool_pick / wq_worker_running
2026/08/22 04:38 upstream 26260251022f 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in kick_pool_pick / wq_worker_running
2026/08/20 22:03 upstream cf62c7084acf 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in kick_pool_pick / wq_worker_running
* Struck through repros no longer work on HEAD.