KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb (6)

Status: moderation: reported on 2026/09/28 04:46
Subsystems: usb
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+21298827560ae41e73b5@syzkaller.appspotmail.com
First crash: 7h51m, last: 7h51m
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
ab6332b6 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb (6) 2026/09/28 05:07 2026/09/28 05:07 2026/09/28 05:59 a3c7249d
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb (3) usb 6 1 789d 789d 0/29 auto-obsoleted due to no activity on 2024/09/03 21:44
upstream KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb (4) usb 6 4 616d 690d 0/29 auto-obsoleted due to no activity on 2025/03/17 03:28
upstream KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb (5) usb 6 2 512d 558d 0/29 auto-obsoleted due to no activity on 2025/06/28 18:56
upstream KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb (2) usb 6 2 869d 874d 0/29 auto-obsoleted due to no activity on 2024/06/15 17:54
upstream KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb usb 6 1 1250d 1250d 0/29 auto-obsoleted due to no activity on 2023/06/01 00:30

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

write to 0xffff8881039c5080 of 4 bytes by task 6488 on cpu 0:
 mon_stop drivers/usb/mon/mon_main.c:166 [inline]
 mon_reader_del+0x1ca/0x260 drivers/usb/mon/mon_main.c:73
 mon_bin_release+0x67/0x120 drivers/usb/mon/mon_bin.c:795
 __fput+0x29e/0x630 fs/file_table.c:512
 ____fput+0x1c/0x30 fs/file_table.c:540
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x1e4/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881039c5080 of 4 bytes by task 37 on cpu 1:
 usbmon_urb_submit include/linux/usb/hcd.h:723 [inline]
 usb_hcd_submit_urb+0x64/0x11f0 drivers/usb/core/hcd.c:1527
 usb_submit_urb+0xaa3/0xbb0 drivers/usb/core/urb.c:586
 usb_start_wait_urb+0x91/0x220 drivers/usb/core/message.c:62
 usb_internal_control_msg drivers/usb/core/message.c:117 [inline]
 usb_control_msg+0x182/0x240 drivers/usb/core/message.c:167
 get_port_status drivers/usb/core/hub.c:607 [inline]
 hub_ext_port_status+0xb4/0x410 drivers/usb/core/hub.c:624
 usb_hub_port_status drivers/usb/core/hub.c:674 [inline]
 port_event drivers/usb/core/hub.c:5774 [inline]
 hub_event+0x47e/0x2aa0 drivers/usb/core/hub.c:5966
 process_one_work kernel/workqueue.c:3396 [inline]
 process_scheduled_works+0x56a/0xa50 kernel/workqueue.c:3479
 worker_thread+0x569/0x750 kernel/workqueue.c:3560
 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: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 37 Comm: kworker/1:1 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: usb_hub_wq hub_event
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/28 04:46 upstream efb44d93a620 a3c7249d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb
* Struck through repros no longer work on HEAD.