[moderation] [block?] KCSAN: data-race in memcpy_and_pad / set_task_ioprio

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a0c83177734a Merge tag 'drm-fixes-2026-03-21' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=173f9e02580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=2e3fa5e1374ebec8a9ad
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [ax...@kernel.dk linux...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/41a0e5c919b7/disk-a0c83177.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/70408718214e/vmlinux-a0c83177.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b610cc9ea81f/bzImage-a0c83177.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2e3fa5...@syzkaller.appspotmail.com

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

write to 0xffff88810d0e88f8 of 8 bytes by task 7165 on cpu 0:
set_task_ioprio+0x24e/0x270 block/blk-ioc.c:280
__do_sys_ioprio_set block/ioprio.c:121 [inline]
__se_sys_ioprio_set+0x24f/0x5a0 block/ioprio.c:65
__x64_sys_ioprio_set+0x43/0x50 block/ioprio.c:65
x64_sys_call+0x2bbf/0x3020 arch/x86/include/generated/asm/syscalls_64.h:252
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810d0e8000 of 3328 bytes by task 7161 on cpu 1:
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+0x6e/0x950 kernel/fork.c:920
copy_process+0x37e/0x20b0 kernel/fork.c:2050
kernel_clone+0x16b/0x5d0 kernel/fork.c:2653
__do_sys_clone3 kernel/fork.c:2955 [inline]
__se_sys_clone3+0x1f5/0x230 kernel/fork.c:2934
__x64_sys_clone3+0x31/0x40 kernel/fork.c:2934
x64_sys_call+0x580/0x3020 arch/x86/include/generated/asm/syscalls_64.h:436
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7161 Comm: syz.0.8700 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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