KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb (4)

Status: moderation: reported C repro on 2026/10/15 22:57
Labels: prio:low race:benign
[Documentation on labels]
Reported-by: syzbot+07e19b8c2cc07b864477@syzkaller.appspotmail.com
First crash: 18h37m, last: 18h37m
▶ ▼ ✨ AI Jobs (3)
ID Workflow Result Correct Bug Created Started Finished Revision
d05e4b01 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb (4) 2026/10/15 22:57 2026/10/15 22:57 2026/10/15 23:37 3f2522c6
d02a774f assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb (4) 2026/10/15 22:57 2026/10/15 22:57 2026/10/15 23:23 3f2522c6
9e651b15 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb (4) 2026/10/15 22:57 2026/10/15 22:57 2026/10/15 23:00 3f2522c6
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb (2) usb 6 4 684d 700d 0/29 auto-obsoleted due to no activity on 2025/01/26 16:15
upstream KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb (3) race:benign prio:low usb 6 1 88d 88d 0/29 auto-obsoleted due to no activity on 2026/09/13 19:05
upstream KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb usb 6 1 944d 944d 0/29 auto-obsoleted due to no activity on 2024/04/19 22:45

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

write to 0xffff888103449080 of 4 bytes by task 3635 on cpu 0:
 mon_reader_add+0xc0/0x1d0 drivers/usb/mon/mon_main.c:47
 mon_bin_open+0x321/0x3a0 drivers/usb/mon/mon_bin.c:722
 chrdev_open+0x2eb/0x3a0 fs/char_dev.c:411
 do_dentry_open+0x49f/0xa60 fs/open.c:996
 vfs_open+0x37/0x1e0 fs/open.c:1101
 do_open fs/namei.c:4866 [inline]
 path_openat+0xc01/0x10d0 fs/namei.c:5029
 do_file_open+0x16c/0x290 fs/namei.c:5058
 do_sys_openat2+0xa0/0x130 fs/open.c:1417
 do_sys_open fs/open.c:1423 [inline]
 __do_sys_openat fs/open.c:1439 [inline]
 __se_sys_openat fs/open.c:1434 [inline]
 __x64_sys_openat+0xf2/0x120 fs/open.c:1434
 x64_sys_call+0x1f72/0x2550 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888103449080 of 4 bytes by task 3636 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
 usbfs_start_wait_urb+0x9f/0x1d0 drivers/usb/core/devio.c:1149
 do_proc_control+0x425/0x850 drivers/usb/core/devio.c:1223
 proc_control+0x71/0xa0 drivers/usb/core/devio.c:1280
 usbdev_do_ioctl drivers/usb/core/devio.c:2648 [inline]
 usbdev_ioctl+0x918/0x16a0 drivers/usb/core/devio.c:2829
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x239d/0x2550 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3636 Comm: syz-executor407 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================
==================================================================
BUG: KCSAN: data-race in mon_reader_del / usb_hcd_submit_urb

write to 0xffff888103449080 of 4 bytes by task 3635 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_close_sync+0xad/0x190 fs/file_table.c:618
 __do_sys_close fs/open.c:1560 [inline]
 __se_sys_close fs/open.c:1545 [inline]
 __x64_sys_close+0x55/0xf0 fs/open.c:1545
 x64_sys_call+0x812/0x2550 arch/x86/include/generated/asm/syscalls_64.h:4
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888103449080 of 4 bytes by task 3636 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
 usbfs_start_wait_urb+0x9f/0x1d0 drivers/usb/core/devio.c:1149
 do_proc_control+0x425/0x850 drivers/usb/core/devio.c:1223
 proc_control+0x71/0xa0 drivers/usb/core/devio.c:1280
 usbdev_do_ioctl drivers/usb/core/devio.c:2648 [inline]
 usbdev_ioctl+0x918/0x16a0 drivers/usb/core/devio.c:2829
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x239d/0x2550 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3636 Comm: syz-executor407 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/15 22:56 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 9aa622dbaab8 a3c7249d .config console log report C ci2-upstream-kcsan-gce KCSAN: data-race in mon_reader_add / usb_hcd_submit_urb
* Struck through repros no longer work on HEAD.