syzbot


KCSAN: data-race in css_set_move_task / memcpy_and_pad (2)

Status: moderation: reported on 2026/01/20 10:41
Subsystems: cgroups
[Documentation on labels]
Reported-by: syzbot+1ee8687806d5edebd5ad@syzkaller.appspotmail.com
First crash: 9d18h, last: 7d09h
Similar bugs (1)
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 245d 245d 0/29 auto-obsoleted due to no activity on 2025/07/24 11:25

Sample crash report:
SELinux: unrecognized netlink message: protocol=4 nlmsg_type=16 sclass=netlink_tcpdiag_socket pid=2258 comm=syz.0.9255
==================================================================
BUG: KCSAN: data-race in css_set_move_task / memcpy_and_pad

write to 0xffff88810d6fec60 of 8 bytes by task 2260 on cpu 1:
 __list_del include/linux/list.h:203 [inline]
 __list_del_entry include/linux/list.h:226 [inline]
 list_del_init include/linux/list.h:295 [inline]
 css_set_move_task+0x212/0x430 kernel/cgroup/cgroup.c:932
 do_cgroup_task_dead kernel/cgroup/cgroup.c:6998 [inline]
 cgroup_task_dead+0x6f/0x2b0 kernel/cgroup/cgroup.c:7062
 finish_task_switch+0x1b1/0x280 kernel/sched/core.c:5156
 context_switch kernel/sched/core.c:5263 [inline]
 __schedule+0x82d/0xc90 kernel/sched/core.c:6867
 __schedule_loop kernel/sched/core.c:6949 [inline]
 schedule+0x5e/0xd0 kernel/sched/core.c:6964
 futex_do_wait kernel/futex/waitwake.c:358 [inline]
 __futex_wait+0x121/0x260 kernel/futex/waitwake.c:687
 futex_wait+0x9c/0x1d0 kernel/futex/waitwake.c:715
 do_futex+0x2bf/0x380 kernel/futex/syscalls.c:130
 __do_sys_futex kernel/futex/syscalls.c:207 [inline]
 __se_sys_futex+0x2f6/0x370 kernel/futex/syscalls.c:188
 __x64_sys_futex+0x78/0x90 kernel/futex/syscalls.c:188
 x64_sys_call+0x2bc2/0x3000 arch/x86/include/generated/asm/syscalls_64.h:203
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810d6fe300 of 3264 bytes by task 2258 on cpu 0:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
 dup_task_struct+0x6e/0x940 kernel/fork.c:919
 copy_process+0x37e/0x1f10 kernel/fork.c:2052
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
 __do_sys_clone kernel/fork.c:2792 [inline]
 __se_sys_clone kernel/fork.c:2776 [inline]
 __x64_sys_clone+0x143/0x180 kernel/fork.c:2776
 x64_sys_call+0x12d0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 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: 2258 Comm: syz.0.9255 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/22 19:39 upstream a66191c590b3 82c9c083 .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
2026/01/20 10:41 upstream 24d479d26b25 06648d9c .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.