[moderation] [kernel?] KCSAN: data-race in copy_process / memcpy_and_pad

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: aef17cb3d3c4 Revert "mm/damon/Kconfig: enable CONFIG_DAMON..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=152c660c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f437300db311c188
dashboard link: https://syzkaller.appspot.com/bug?extid=69f855c414abdeabe723
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
CC: [Liam.H...@oracle.com ak...@linux-foundation.org bse...@google.com da...@redhat.com dietmar....@arm.com juri....@redhat.com ke...@kernel.org linux-...@vger.kernel.org linu...@kvack.org lorenzo...@oracle.com mgo...@suse.de mho...@suse.com mi...@redhat.com pet...@infradead.org ros...@goodmis.org rp...@kernel.org sur...@google.com vba...@suse.cz vincent...@linaro.org vsch...@redhat.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3b021b9f4a41/disk-aef17cb3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ff546f3d73c4/vmlinux-aef17cb3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/07044c10f149/bzImage-aef17cb3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+69f855...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in copy_process / memcpy_and_pad

write to 0xffff8881001d15f8 of 8 bytes by task 3865 on cpu 0:
__list_add include/linux/list.h:153 [inline]
list_add_tail include/linux/list.h:183 [inline]
copy_process+0x1d42/0x1fe0 kernel/fork.c:2384
kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
user_mode_thread+0x7d/0xb0 kernel/fork.c:2677
call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3321
worker_thread+0x582/0x770 kernel/workqueue.c:3402
kthread+0x486/0x510 kernel/kthread.c:464
ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881001d1040 of 3200 bytes by task 2 on cpu 1:
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:873
copy_process+0x399/0x1fe0 kernel/fork.c:1999
kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
kernel_thread+0xac/0xe0 kernel/fork.c:2661
create_kthread kernel/kthread.c:487 [inline]
kthreadd+0x28d/0x360 kernel/kthread.c:847
ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2 Comm: kthreadd Tainted: G W 6.16.0-rc1-syzkaller-00004-gaef17cb3d3c4 #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.