KCSAN: data-race in __set_task_comm / strlen (2)

Status: moderation: reported on 2026/08/04 08:46
Subsystems: fs
Labels: race:benign prio:low
[Documentation on labels]
Reported-by: syzbot+98baf51f5cc36dcbe2f7@syzkaller.appspotmail.com
First crash: 10d, last: 7m
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
736576bd assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ KCSAN: data-race in __set_task_comm / strlen (2) 2026/08/09 11:33 2026/08/09 11:33 2026/08/09 12:12 5d63f80b
9011fcab assessment-kcsan Benign: ✅ KCSAN: data-race in __set_task_comm / strlen (2) 2026/08/04 08:45 2026/08/04 08:45 2026/08/04 09:18 9451e17e
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __set_task_comm / strlen fs mm 6 9 169d 339d 0/29 auto-obsoleted due to no activity on 2026/04/23 17:03

Sample crash report:
8021q: adding VLAN 0 to HW filter on device eth22
==================================================================
BUG: KCSAN: data-race in __set_task_comm / strlen

write to 0xffff88810489de18 of 8 bytes by task 6257 on cpu 1:
 __set_task_comm+0x78/0x180 fs/exec.c:1099
 begin_new_exec+0xeb4/0x1210 fs/exec.c:1257
 load_elf_binary+0x64a/0x1a30 fs/binfmt_elf.c:1010
 search_binary_handler fs/exec.c:1694 [inline]
 exec_binprm fs/exec.c:1726 [inline]
 bprm_execve+0x45c/0x9b0 fs/exec.c:1778
 kernel_execve+0x5e0/0x630 fs/exec.c:1922
 call_usermodehelper_exec_async+0x196/0x250 kernel/umh.c:109
 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 0xffff88810489de19 of 1 bytes by task 3020 on cpu 0:
 strlen+0x19/0x40 lib/string.c:402
 __fortify_strlen include/linux/fortify-string.h:218 [inline]
 trace_event_get_offsets_sched_stat_runtime include/trace/events/sched.h:560 [inline]
 do_trace_event_raw_event_sched_stat_runtime include/trace/events/sched.h:553 [inline]
 trace_event_raw_event_sched_stat_runtime+0x59/0x140 include/trace/events/sched.h:553
 __do_trace_sched_stat_runtime include/trace/events/sched.h:576 [inline]
 trace_sched_stat_runtime include/trace/events/sched.h:576 [inline]
 update_se+0x153/0x460 kernel/sched/fair.c:1375
 update_curr+0x29/0x210 kernel/sched/fair.c:2001
 dequeue_entity kernel/sched/fair.c:6239 [inline]
 dequeue_entities+0xb6/0xca0 kernel/sched/fair.c:7951
 dequeue_task_fair+0x4a/0xb0 kernel/sched/fair.c:8046
 detach_task+0x37/0x80 kernel/sched/fair.c:10852
 detach_tasks kernel/sched/fair.c:10992 [inline]
 sched_balance_rq+0x1a34/0x20a0 kernel/sched/fair.c:13349
 sched_balance_newidle kernel/sched/fair.c:14433 [inline]
 pick_task_fair+0x2a7/0x4b0 kernel/sched/fair.c:9948
 __pick_next_task kernel/sched/core.c:6144 [inline]
 pick_next_task kernel/sched/core.c:6674 [inline]
 __schedule+0x37b/0xd10 kernel/sched/core.c:7149
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x5a/0xa0 kernel/sched/core.c:7326
 schedule_hrtimeout_range_clock+0x126/0x1a0 kernel/time/sleep_timeout.c:207
 schedule_hrtimeout_range+0x28/0x40 kernel/time/sleep_timeout.c:263
 poll_schedule_timeout fs/select.c:241 [inline]
 do_poll fs/select.c:965 [inline]
 do_sys_poll+0xa40/0xc00 fs/select.c:1015
 __do_sys_ppoll fs/select.c:1112 [inline]
 __se_sys_ppoll+0x1e2/0x220 fs/select.c:1092
 __x64_sys_ppoll+0x67/0x80 fs/select.c:1092
 x64_sys_call+0x28d3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:272
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x77 -> 0x6f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3020 Comm: dhcpcd Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
==================================================================
8021q: adding VLAN 0 to HW filter on device eth23
8021q: adding VLAN 0 to HW filter on device eth24
8021q: adding VLAN 0 to HW filter on device eth25
8021q: adding VLAN 0 to HW filter on device eth4
8021q: adding VLAN 0 to HW filter on device eth26
8021q: adding VLAN 0 to HW filter on device eth27
8021q: adding VLAN 0 to HW filter on device eth1
8021q: adding VLAN 0 to HW filter on device eth2
8021q: adding VLAN 0 to HW filter on device eth3

Crashes (15):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/15 02:20 upstream dac3e89a2c90 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/14 22:27 upstream ad8d485e6658 6f9b3e89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/14 22:10 upstream ad8d485e6658 6f9b3e89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/14 00:54 upstream 3aa1dcaa4f6f b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/12 21:46 upstream 3d6d817622b0 359b2492 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/11 12:13 upstream d58772d8520c 508909ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/09 08:58 upstream 06cf61899d64 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/08 20:32 upstream a7c7074b58d2 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/08 10:15 upstream bcc44b6785f2 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/08 03:09 upstream bcc44b6785f2 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/08 03:06 upstream bcc44b6785f2 e4ef95d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/06 23:46 upstream fcaeecb8b0cd c38879ea .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/06 06:17 upstream 0d8395707651 cd5b1963 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/05 10:07 upstream c21bb4193868 52aa2820 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
2026/08/04 08:45 upstream 848acc8ffe1b 9451e17e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __set_task_comm / strlen
* Struck through repros no longer work on HEAD.