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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4a26e7032d7d Merge tag 'core-bugs-2025-12-01' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=147314c2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1cf5676573a33318
dashboard link: https://syzkaller.appspot.com/bug?extid=ca2cb2fbd1e035a79a9b
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
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/d6da4f1044e5/disk-4a26e703.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ee614a58c06e/vmlinux-4a26e703.xz
kernel image: https://storage.googleapis.com/syzbot-assets/43cbdf4a8d4f/bzImage-4a26e703.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ca2cb2...@syzkaller.appspotmail.com

loop6: detected capacity change from 0 to 2048
loop6: p1 < > p4
loop6: p4 size 8388608 extends beyond EOD, truncated
==================================================================
BUG: KCSAN: data-race in iter_file_splice_write / set_task_ioprio

write to 0xffff88813ea929d0 of 8 bytes by task 24437 on cpu 1:
set_task_ioprio+0x24f/0x270 block/blk-ioc.c:280
__do_sys_ioprio_set block/ioprio.c:121 [inline]
__se_sys_ioprio_set+0x250/0x5a0 block/ioprio.c:65
__x64_sys_ioprio_set+0x43/0x50 block/ioprio.c:65
x64_sys_call+0x2781/0x3000 arch/x86/include/generated/asm/syscalls_64.h:252
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88813ea929d0 of 8 bytes by task 24438 on cpu 0:
__get_task_ioprio include/linux/ioprio.h:59 [inline]
get_current_ioprio include/linux/ioprio.h:84 [inline]
init_sync_kiocb include/linux/fs.h:2177 [inline]
iter_file_splice_write+0x44f/0xa20 fs/splice.c:736
do_splice_from fs/splice.c:938 [inline]
direct_splice_actor+0x156/0x2a0 fs/splice.c:1161
splice_direct_to_actor+0x312/0x680 fs/splice.c:1105
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0xda/0x150 fs/splice.c:1230
do_sendfile+0x380/0x650 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64 fs/read_write.c:1417 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1417
x64_sys_call+0x2db1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0xffff88811e4e5770

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 24438 Comm: syz.6.7292 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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