[moderation] [block?] KCSAN: data-race in __bio_queue_enter / blk_mq_unfreeze_queue_nomemrestore (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f1a5e78a55eb Merge tag 'drm-fixes-2026-05-02' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1174cf6c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=c392d7f25c4cb962cf09
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/c3d400c77c74/disk-f1a5e78a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca502903f1d9/vmlinux-f1a5e78a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/04b85e8c153a/bzImage-f1a5e78a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c392d7...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __bio_queue_enter / blk_mq_unfreeze_queue_nomemrestore

read-write to 0xffff888101f34db4 of 4 bytes by task 4500 on cpu 1:
__blk_mq_unfreeze_queue block/blk-mq.c:218 [inline]
blk_mq_unfreeze_queue_nomemrestore+0x38/0xc0 block/blk-mq.c:232
blk_mq_unfreeze_queue include/linux/blk-mq.h:962 [inline]
loop_set_status+0x3a2/0x6a0 drivers/block/loop.c:1266
loop_set_status_old drivers/block/loop.c:1362 [inline]
lo_ioctl+0x799/0x13a0 drivers/block/loop.c:1551
blkdev_ioctl+0x387/0x460 block/ioctl.c:797
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888101f34db4 of 4 bytes by task 4497 on cpu 0:
__bio_queue_enter+0x279/0x5a0 block/blk-core.c:353
bio_queue_enter block/blk.h:93 [inline]
blk_mq_submit_bio+0x198/0x1130 block/blk-mq.c:3175
__submit_bio+0x103/0x4f0 block/blk-core.c:635
__submit_bio_noacct_mq block/blk-core.c:722 [inline]
submit_bio_noacct_nocheck+0x153/0x620 block/blk-core.c:753
submit_bio_noacct+0x746/0x980 block/blk-core.c:884
submit_bio+0x2a4/0x2c0 block/blk-core.c:926
mpage_bio_submit_read fs/mpage.c:74 [inline]
mpage_readahead+0x295/0x2e0 fs/mpage.c:379
blkdev_readahead+0x1c/0x30 block/fops.c:499
read_pages+0xa3/0x480 mm/readahead.c:163
page_cache_ra_unbounded+0x357/0x420 mm/readahead.c:304
do_page_cache_ra mm/readahead.c:334 [inline]
page_cache_ra_order+0x153/0x220 mm/readahead.c:538
page_cache_async_ra+0x383/0x4b0 mm/readahead.c:700
filemap_readahead mm/filemap.c:2664 [inline]
filemap_get_pages+0x596/0x1250 mm/filemap.c:2710
filemap_splice_read+0x3c6/0x780 mm/filemap.c:3085
do_splice_read fs/splice.c:980 [inline]
splice_direct_to_actor+0x26e/0x670 fs/splice.c:1084
do_splice_direct_actor fs/splice.c:1202 [inline]
do_splice_direct+0x119/0x1a0 fs/splice.c:1228
do_sendfile+0x382/0x650 fs/read_write.c:1372
__do_sys_sendfile64 fs/read_write.c:1433 [inline]
__se_sys_sendfile64 fs/read_write.c:1419 [inline]
__x64_sys_sendfile64+0x105/0x150 fs/read_write.c:1419
x64_sys_call+0x2dc4/0x3020 arch/x86/include/generated/asm/syscalls_64.h:41
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 4497 Comm: syz.5.241 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================
syz.5.241 (4497) used greatest stack depth: 10008 bytes left


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