[moderation] [block?] KCSAN: data-race in lo_ioctl / loop_queue_rq (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 610a9b8f49fb Linux 6.7-rc8
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d1326ee80000
kernel config: https://syzkaller.appspot.com/x/.config?x=17e138c8fc533c5e
dashboard link: https://syzkaller.appspot.com/bug?extid=df2b8b0a683bf8e3b643
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/238dea1fdecf/disk-610a9b8f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c4adb81883c3/vmlinux-610a9b8f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ad74642e2389/bzImage-610a9b8f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+df2b8b...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in lo_ioctl / loop_queue_rq

write to 0xffff888100c0f478 of 4 bytes by task 21165 on cpu 1:
loop_clr_fd drivers/block/loop.c:1254 [inline]
lo_ioctl+0xe69/0x12e0 drivers/block/loop.c:1563
blkdev_ioctl+0x375/0x460 block/ioctl.c:633
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888100c0f478 of 4 bytes by task 21160 on cpu 0:
loop_queue_rq+0x55/0x650 drivers/block/loop.c:1853
__blk_mq_issue_directly block/blk-mq.c:2590 [inline]
blk_mq_request_issue_directly+0x1d6/0x330 block/blk-mq.c:2675
blk_mq_plug_issue_direct+0x156/0x520 block/blk-mq.c:2696
blk_mq_flush_plug_list+0x2b6/0xdc0 block/blk-mq.c:2805
__blk_flush_plug+0x210/0x260 block/blk-core.c:1150
blk_finish_plug+0x47/0x60 block/blk-core.c:1174
do_writepages+0x21a/0x340 mm/page-writeback.c:2560
filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:387
__filemap_fdatawrite_range mm/filemap.c:420 [inline]
file_write_and_wait_range+0xf4/0x190 mm/filemap.c:778
blkdev_fsync+0x4e/0xa0 block/fops.c:529
vfs_fsync_range+0x111/0x120 fs/sync.c:188
generic_write_sync+0xf2/0x120 include/linux/fs.h:2653
blkdev_write_iter+0x364/0x390 block/fops.c:700
do_iter_write+0x4ad/0x770 fs/read_write.c:860
vfs_iter_write+0x56/0x70 fs/read_write.c:901
iter_file_splice_write+0x462/0x7e0 fs/splice.c:736
do_splice_from fs/splice.c:933 [inline]
direct_splice_actor+0x8a/0xb0 fs/splice.c:1142
splice_direct_to_actor+0x31d/0x690 fs/splice.c:1088
do_splice_direct+0x10d/0x190 fs/splice.c:1194
do_sendfile+0x3c4/0x980 fs/read_write.c:1254
__do_sys_sendfile64 fs/read_write.c:1322 [inline]
__se_sys_sendfile64 fs/read_write.c:1308 [inline]
__x64_sys_sendfile64+0x110/0x150 fs/read_write.c:1308
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21160 Comm: syz-executor.1 Not tainted 6.7.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================
I/O error, dev loop7, sector 1344 op 0x1:(WRITE) flags 0x800 phys_seg 1 prio class 2
Buffer I/O error on dev loop7, logical block 168, lost async page write
Buffer I/O error on dev loop7, logical block 167, lost async page write
Buffer I/O error on dev loop7, logical block 166, lost async page write
Buffer I/O error on dev loop7, logical block 165, lost async page write
Buffer I/O error on dev loop7, logical block 164, lost async page write
Buffer I/O error on dev loop7, logical block 163, lost async page write
Buffer I/O error on dev loop7, logical block 162, lost async page write
Buffer I/O error on dev loop7, logical block 161, lost async page write
Buffer I/O error on dev loop7, logical block 160, lost async page write


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[syzbot]

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