syzbot


KCSAN: data-race in dequeue_signal / ptrace_check_attach (12)

Status: moderation: reported on 2026/04/24 13:36
Subsystems: kernel
[Documentation on labels]
Reported-by: syzbot+317772dacbc1ea722bd2@syzkaller.appspotmail.com
First crash: 1d16h, last: 1d16h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
00347d9b-05f5-456c-927c-ddd0eb7aefef assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in dequeue_signal / ptrace_check_attach (12) 2026/04/24 13:35 2026/04/24 13:35 2026/04/24 13:56 9cfb3ca710b61b2f1e2032fa6d94d4a00f81ab36
Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (6) kernel 6 1 927d 927d 0/29 auto-obsoleted due to no activity on 2023/11/16 03:30
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (10) kernel 6 1 563d 563d 0/29 auto-obsoleted due to no activity on 2024/11/13 22:28
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (7) kernel 6 13 763d 866d 0/29 auto-obsoleted due to no activity on 2024/04/27 21:52
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (5) kernel 6 3 965d 1028d 0/29 auto-obsoleted due to no activity on 2023/10/08 11:58
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (3) kernel 6 3 1151d 1175d 0/29 auto-obsoleted due to no activity on 2023/04/16 11:35
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (11) kernel 6 35 73d 526d 0/29 auto-obsoleted due to no activity on 2026/04/08 23:50
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (2) kernel 6 1 1220d 1220d 0/29 auto-obsoleted due to no activity on 2023/02/02 07:54
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (9) kernel 6 1 628d 628d 0/29 auto-obsoleted due to no activity on 2024/09/09 07:15
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach kernel 6 1 1323d 1323d 0/29 auto-obsoleted due to no activity on 2022/10/15 10:03
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (4) kernel 6 2 1090d 1098d 0/29 auto-obsoleted due to no activity on 2023/06/06 04:16
upstream KCSAN: data-race in dequeue_signal / ptrace_check_attach (8) kernel 6 2 707d 728d 0/29 auto-obsoleted due to no activity on 2024/06/22 14:38

Sample crash report:
UDC core: USB Raw Gadget: couldn't find an available UDC or it's busy
misc raw-gadget: fail, usb_gadget_register_driver returned -16
==================================================================
BUG: KCSAN: data-race in dequeue_signal / ptrace_check_attach

read-write to 0xffff88815484eb98 of 8 bytes by task 30405 on cpu 0:
 dequeue_signal+0x308/0x3a0 kernel/signal.c:656
 get_signal+0x375/0xf20 kernel/signal.c:2917
 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:98
 __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:238 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x232/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88815484eb98 of 8 bytes by task 30399 on cpu 1:
 ptrace_freeze_traced kernel/ptrace.c:189 [inline]
 ptrace_check_attach+0xa9/0x280 kernel/ptrace.c:256
 __do_sys_ptrace kernel/ptrace.c:1410 [inline]
 __se_sys_ptrace+0xd3/0x2c0 kernel/ptrace.c:1388
 __x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1388
 x64_sys_call+0x287b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:102
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000008010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 30399 Comm: syz.5.8267 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/24 13:35 upstream dd6c438c3e64 1c2b9291 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in dequeue_signal / ptrace_check_attach
* Struck through repros no longer work on HEAD.