syzbot


KCSAN: data-race in css_set_move_task / memcpy_and_pad (3)

Status: moderation: reported on 2026/07/08 00:24
Subsystems: cgroups
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+2d033bf8519b4b95dbb7@syzkaller.appspotmail.com
First crash: 16h52m, last: 16h52m
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
726858d1-e2ad-468e-b69c-c3fa2ac17bfe assessment-kcsan Benign: ✅ KCSAN: data-race in css_set_move_task / memcpy_and_pad (3) 2026/07/08 00:30 2026/07/08 00:30 2026/07/08 01:03 93f579545ae410f5bccfa141d2e7bf03178f036c

			
		
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in css_set_move_task / memcpy_and_pad cgroups 6 1 405d 405d 0/29 auto-obsoleted due to no activity on 2025/07/24 11:25
upstream KCSAN: data-race in css_set_move_task / memcpy_and_pad (2) cgroups prio:low 6 6 97d 169d 0/29 auto-obsoleted due to no activity on 2026/05/28 13:33

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

write to 0xffff888101dde018 of 8 bytes by task 22 on cpu 1:
 __list_del include/linux/list.h:226 [inline]
 __list_del_entry include/linux/list.h:249 [inline]
 list_del_init include/linux/list.h:318 [inline]
 css_set_move_task+0x1c1/0x380 kernel/cgroup/cgroup.c:909
 do_cgroup_task_dead kernel/cgroup/cgroup.c:7076 [inline]
 cgroup_task_dead+0x6f/0x2b0 kernel/cgroup/cgroup.c:7140
 finish_task_switch+0x26e/0x340 kernel/sched/core.c:5405
 context_switch kernel/sched/core.c:5513 [inline]
 __schedule+0x799/0xd10 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0x5a/0xa0 kernel/sched/core.c:7326
 smpboot_thread_fn+0x36f/0x510 kernel/smpboot.c:156
 kthread+0x221/0x270 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

read to 0xffff888101ddd640 of 3456 bytes by task 9328 on cpu 0:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1008
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
 dup_task_struct+0x6d/0x6a0 kernel/fork.c:925
 copy_process+0x5a0/0x2310 kernel/fork.c:2115
 kernel_clone+0x1c0/0x5f0 kernel/fork.c:2748
 __do_sys_clone kernel/fork.c:2889 [inline]
 __se_sys_clone kernel/fork.c:2873 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2873
 x64_sys_call+0x1222/0x3020 arch/x86/include/generated/asm/syscalls_64.h:57
 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

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9328 Comm: dhcpcd-run-hook Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/08 00:23 upstream 0e35b9b6ec0f 76cdc0c0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in css_set_move_task / memcpy_and_pad
* Struck through repros no longer work on HEAD.