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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 07e27ad16399 Linux 6.17-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1179a8e2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=834cde88fbe9577868d7
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [b...@alien8.de dave....@linux.intel.com h...@zytor.com linux-...@vger.kernel.org mi...@redhat.com tg...@linutronix.de x...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/13f1b7910f3d/disk-07e27ad1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0a177c590a0f/vmlinux-07e27ad1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2ca3d6e8d07f/bzImage-07e27ad1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+834cde...@syzkaller.appspotmail.com

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

write to 0xffff88810ac2465c of 4 bytes by task 28 on cpu 1:
trc_wait_for_one_reader+0x283/0x3c0 kernel/rcu/tasks.h:1756
check_all_holdout_tasks_trace+0xcb/0x4b0 kernel/rcu/tasks.h:1946
rcu_tasks_wait_gp+0x3fa/0x530 kernel/rcu/tasks.h:885
rcu_tasks_one_gp+0x7f3/0x8e0 kernel/rcu/tasks.h:622
rcu_tasks_kthread+0xf7/0x110 kernel/rcu/tasks.h:658
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x11f/0x1b0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff88810ac24200 of 3264 bytes by task 8419 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:877
copy_process+0x399/0x2000 kernel/fork.c:2004
kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
__do_sys_clone3 kernel/fork.c:2909 [inline]
__se_sys_clone3+0x1c2/0x200 kernel/fork.c:2888
__x64_sys_clone3+0x31/0x40 kernel/fork.c:2888
x64_sys_call+0x1fc9/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:436
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: 8419 Comm: syz.3.1619 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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