[moderation] [block?] KCSAN: data-race in blk_mq_start_request / bt_tags_for_each (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 045395d86acd Merge tag 'cgroup-for-6.9' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=169704b6180000
kernel config: https://syzkaller.appspot.com/x/.config?x=c2e78057edf4dcbf
dashboard link: https://syzkaller.appspot.com/bug?extid=42453004889f6113dfb7
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/5972e70d4795/disk-045395d8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a597cfa200b6/vmlinux-045395d8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a712c47f7d45/bzImage-045395d8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+424530...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in blk_mq_start_request / bt_tags_for_each

write to 0xffff888102416558 of 8 bytes by task 26516 on cpu 0:
blk_mq_start_request+0x220/0x380 block/blk-mq.c:1267
scsi_queue_rq+0x14a3/0x1a00 drivers/scsi/scsi_lib.c:1759
blk_mq_dispatch_rq_list+0x2d9/0x10a0 block/blk-mq.c:2058
__blk_mq_do_dispatch_sched block/blk-mq-sched.c:170 [inline]
blk_mq_do_dispatch_sched block/blk-mq-sched.c:184 [inline]
__blk_mq_sched_dispatch_requests+0x5ec/0xd20 block/blk-mq-sched.c:309
blk_mq_sched_dispatch_requests+0x78/0xe0 block/blk-mq-sched.c:331
blk_mq_run_hw_queue+0x298/0x4c0 block/blk-mq.c:2273
blk_mq_get_tag+0x479/0x590 block/blk-mq-tag.c:170
__blk_mq_alloc_requests+0x6c6/0xbf0 block/blk-mq.c:499
blk_mq_get_new_requests block/blk-mq.c:2891 [inline]
blk_mq_submit_bio+0x6b7/0xdb0 block/blk-mq.c:2989
__submit_bio+0x11c/0x350 block/blk-core.c:619
__submit_bio_noacct_mq block/blk-core.c:698 [inline]
submit_bio_noacct_nocheck+0x501/0x6a0 block/blk-core.c:727
submit_bio_noacct+0x67d/0x830 block/blk-core.c:837
submit_bio+0x212/0x220 block/blk-core.c:879
ext4_io_submit+0x8a/0xa0 fs/ext4/page-io.c:378
ext4_do_writepages+0xb3a/0x2100 fs/ext4/inode.c:2699
ext4_writepages+0x15e/0x2e0 fs/ext4/inode.c:2768
do_writepages+0x1c2/0x340 mm/page-writeback.c:2553
filemap_fdatawrite_wbc+0xdb/0xf0 mm/filemap.c:388
__filemap_fdatawrite_range mm/filemap.c:421 [inline]
__filemap_fdatawrite mm/filemap.c:427 [inline]
filemap_flush+0x95/0xc0 mm/filemap.c:454
ext4_alloc_da_blocks+0x50/0x130 fs/ext4/inode.c:3072
ext4_release_file+0x5f/0x1c0 fs/ext4/file.c:169
__fput+0x299/0x630 fs/file_table.c:423
____fput+0x15/0x20 fs/file_table.c:451
task_work_run+0x135/0x1a0 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x5fc/0x1740 kernel/exit.c:878
do_group_exit+0x101/0x150 kernel/exit.c:1027
get_signal+0xf4e/0x10a0 kernel/signal.c:2907
arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:105 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
irqentry_exit_to_user_mode+0x8f/0x120 kernel/entry/common.c:225
irqentry_exit+0x12/0x40 kernel/entry/common.c:328
exc_general_protection+0x33b/0x4c0 arch/x86/kernel/traps.c:643
asm_exc_general_protection+0x26/0x30 arch/x86/include/asm/idtentry.h:564

read to 0xffff888102416558 of 8 bytes by task 24 on cpu 1:
blk_mq_find_and_get_req block/blk-mq-tag.c:259 [inline]
bt_tags_iter block/blk-mq-tag.c:356 [inline]
__sbitmap_for_each_set include/linux/sbitmap.h:281 [inline]
sbitmap_for_each_set include/linux/sbitmap.h:302 [inline]
bt_tags_for_each+0x2cc/0x500 block/blk-mq-tag.c:391
__blk_mq_all_tag_iter block/blk-mq-tag.c:402 [inline]
blk_mq_tagset_busy_iter+0x114/0x150 block/blk-mq-tag.c:446
scsi_host_busy+0x4f/0x80 drivers/scsi/hosts.c:604
scsi_host_queue_ready drivers/scsi/scsi_lib.c:1343 [inline]
scsi_queue_rq+0x2f3/0x1a00 drivers/scsi/scsi_lib.c:1737
blk_mq_dispatch_rq_list+0x2d9/0x10a0 block/blk-mq.c:2058
__blk_mq_sched_dispatch_requests+0x1ce/0xd20 block/blk-mq-sched.c:301
blk_mq_sched_dispatch_requests+0x78/0xe0 block/blk-mq-sched.c:331
blk_mq_run_hw_queue+0x298/0x4c0 block/blk-mq.c:2273
blk_mq_run_hw_queues+0x15b/0x1e0 block/blk-mq.c:2322
blk_mq_requeue_work+0x408/0x430 block/blk-mq.c:1491
process_one_work kernel/workqueue.c:3254 [inline]
process_scheduled_works+0x460/0x980 kernel/workqueue.c:3335
worker_thread+0x525/0x730 kernel/workqueue.c:3416
kthread+0x1d7/0x210 kernel/kthread.c:388
ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:243

value changed: 0xffff888102c9e6c0 -> 0xffff888102c71d40

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24 Comm: kworker/1:0H Not tainted 6.8.0-syzkaller-00711-g045395d86acd #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Workqueue: kblockd blk_mq_requeue_work
==================================================================


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[syzbot]

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