syzbot


KCSAN: data-race in __flush_work / __flush_work

Status: moderation: reported on 2024/06/14 08:38
Subsystems: io-uring
[Documentation on labels]
Reported-by: syzbot+a01f9ad56c5313abfa64@syzkaller.appspotmail.com
First crash: 34d, last: 34d

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

write to 0xffff88812911c3f0 of 8 bytes by task 26688 on cpu 0:
 instrument_write include/linux/instrumented.h:41 [inline]
 ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline]
 insert_wq_barrier kernel/workqueue.c:3793 [inline]
 start_flush_work kernel/workqueue.c:4145 [inline]
 __flush_work+0x30b/0x570 kernel/workqueue.c:4181
 flush_work kernel/workqueue.c:4232 [inline]
 flush_delayed_work+0x66/0x70 kernel/workqueue.c:4254
 io_fallback_tw+0x24b/0x320 io_uring/io_uring.c:1136
 tctx_task_work_run+0xd1/0x1b0 io_uring/io_uring.c:1148
 tctx_task_work+0x40/0x80 io_uring/io_uring.c:1173
 task_work_run+0x13a/0x1a0 kernel/task_work.c:180
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x5d5/0x1710 kernel/exit.c:874
 do_group_exit+0x102/0x150 kernel/exit.c:1023
 get_signal+0xf2f/0x1080 kernel/signal.c:2909
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88812911c3f0 of 8 bytes by task 26365 on cpu 1:
 __flush_work+0x42a/0x570 kernel/workqueue.c:4191
 flush_work kernel/workqueue.c:4232 [inline]
 flush_delayed_work+0x66/0x70 kernel/workqueue.c:4254
 io_uring_try_cancel_requests+0x35b/0x370 io_uring/io_uring.c:3037
 io_ring_exit_work+0x148/0x500 io_uring/io_uring.c:2816
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x730 kernel/workqueue.c:3393
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x0000000000400000 -> 0xffff88810006c005

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26365 Comm: kworker/u8:16 Tainted: G        W          6.10.0-rc3-syzkaller-00099-gd20f6b3d747c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Workqueue: iou_exit io_ring_exit_work
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/06/14 08:37 upstream d20f6b3d747c a9616ff5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __flush_work / __flush_work
* Struck through repros no longer work on HEAD.