syzbot


KCSAN: data-race in css_set_move_task / memcpy_and_pad

Status: moderation: reported on 2025/05/29 11:25
Subsystems: cgroups
[Documentation on labels]
Reported-by: syzbot+061798cb1c5aaaae60d3@syzkaller.appspotmail.com
First crash: 10d, last: 10d

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

write to 0xffff88810a2d8958 of 8 bytes by task 18899 on cpu 1:
 __list_del include/linux/list.h:195 [inline]
 __list_del_entry include/linux/list.h:218 [inline]
 list_del_init include/linux/list.h:287 [inline]
 css_set_move_task+0x212/0x430 kernel/cgroup/cgroup.c:903
 cgroup_exit+0x6b/0x350 kernel/cgroup/cgroup.c:6832
 do_exit+0x5f5/0x16f0 kernel/exit.c:971
 do_group_exit+0x139/0x140 kernel/exit.c:1108
 __do_sys_exit_group kernel/exit.c:1119 [inline]
 __se_sys_exit_group kernel/exit.c:1117 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1117
 x64_sys_call+0x2fa4/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810a2d8000 of 3200 bytes by task 18900 on cpu 0:
 memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
 arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:98
 dup_task_struct+0x83/0x6a0 kernel/fork.c:1133
 copy_process+0x399/0x1fe0 kernel/fork.c:2259
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2859
 __do_sys_clone kernel/fork.c:3002 [inline]
 __se_sys_clone kernel/fork.c:2986 [inline]
 __x64_sys_clone+0xe6/0x120 kernel/fork.c:2986
 x64_sys_call+0x2c59/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 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: 18900 Comm: dhcpcd-run-hook Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/29 11:24 upstream 90b83efa6701 3d2f584d .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.