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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ab0a97cffa0b Merge tag 'powerpc-6.8-4' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12ccca02180000
kernel config: https://syzkaller.appspot.com/x/.config?x=7507056e4ee79a
dashboard link: https://syzkaller.appspot.com/bug?extid=f3d1ce7f36ed50bd8941
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/786f1e630b29/disk-ab0a97cf.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0535b9d0e624/vmlinux-ab0a97cf.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2f3bbc61c7ec/bzImage-ab0a97cf.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f3d1ce...@syzkaller.appspotmail.com

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

write to 0xffff888102d757e0 of 4 bytes by task 2273 on cpu 0:
blk_mq_rq_ctx_init+0x18d/0x2f0 block/blk-mq.c:370
__blk_mq_alloc_requests+0x7c8/0xa40 block/blk-mq.c:516
blk_mq_get_new_requests block/blk-mq.c:2905 [inline]
blk_mq_submit_bio+0x417/0xe30 block/blk-mq.c:3001
__submit_bio+0x11c/0x350 block/blk-core.c:608
__submit_bio_noacct_mq block/blk-core.c:687 [inline]
submit_bio_noacct_nocheck+0x4ad/0x5e0 block/blk-core.c:716
submit_bio_noacct+0x67d/0x830 block/blk-core.c:826
submit_bio+0x212/0x220 block/blk-core.c:868
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:376
____fput+0x15/0x20 fs/file_table.c:404
task_work_run+0x135/0x1a0 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x604/0x16d0 kernel/exit.c:871
do_group_exit+0x101/0x150 kernel/exit.c:1020
get_signal+0xf4e/0x10a0 kernel/signal.c:2893
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+0x9c/0x130 kernel/entry/common.c:225
irqentry_exit+0x12/0x40 kernel/entry/common.c:328
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

read to 0xffff888102d757e0 of 4 bytes by task 2264 on cpu 1:
blk_mq_find_and_get_req block/blk-mq-tag.c:260 [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+0x2e2/0x500 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:2070
__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:2285
blk_mq_flush_plug_list+0x7a7/0xdc0 block/blk-mq.c:2833
blk_add_rq_to_plug+0x102/0x3d0 block/blk-mq.c:1299
blk_mq_submit_bio+0x5c8/0xe30 block/blk-mq.c:3027
__submit_bio+0x11c/0x350 block/blk-core.c:608
__submit_bio_noacct_mq block/blk-core.c:687 [inline]
submit_bio_noacct_nocheck+0x4ad/0x5e0 block/blk-core.c:716
submit_bio_noacct+0x67d/0x830 block/blk-core.c:826
submit_bio+0x212/0x220 block/blk-core.c:868
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:376
____fput+0x15/0x20 fs/file_table.c:404
task_work_run+0x135/0x1a0 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x604/0x16d0 kernel/exit.c:871
do_group_exit+0x101/0x150 kernel/exit.c:1020
get_signal+0xf4e/0x10a0 kernel/signal.c:2893
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+0x9c/0x130 kernel/entry/common.c:225
irqentry_exit+0x12/0x40 kernel/entry/common.c:328
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

value changed: 0x00001d25 -> 0xffffffff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2264 Comm: syz-executor.1 Not tainted 6.8.0-rc5-syzkaller-00329-gab0a97cffa0b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

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