[moderation] [block?] KCSAN: data-race in __blk_mq_sched_dispatch_requests / blk_mq_dispatch_rq_list (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 63676eefb7a0 Merge tag 'sched_ext-for-6.13-rc5-fixes' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1333b1c4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c5e179f449c1ff36
dashboard link: https://syzkaller.appspot.com/bug?extid=d27c8cc9338dfe5e6b38
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/867eb8fde4e1/disk-63676eef.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a4c43dfe0999/vmlinux-63676eef.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9b651cd4799d/bzImage-63676eef.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d27c8c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __blk_mq_sched_dispatch_requests / blk_mq_dispatch_rq_list

write to 0xffff8881023cc4f8 of 4 bytes by task 25 on cpu 1:
blk_mq_dispatch_rq_list+0xd99/0xfa0
__blk_mq_sched_dispatch_requests+0x1ce/0xd50 block/blk-mq-sched.c:301
blk_mq_sched_dispatch_requests+0x88/0x120 block/blk-mq-sched.c:331
blk_mq_run_hw_queue+0x18a/0x230 block/blk-mq.c:2352
blk_mq_run_hw_queues+0x1ac/0x240 block/blk-mq.c:2401
blk_mq_requeue_work+0x3a5/0x3d0 block/blk-mq.c:1566
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff8881023cc4f8 of 4 bytes by task 19542 on cpu 0:
__blk_mq_do_dispatch_sched block/blk-mq-sched.c:97 [inline]
blk_mq_do_dispatch_sched block/blk-mq-sched.c:184 [inline]
__blk_mq_sched_dispatch_requests+0x28b/0xd50 block/blk-mq-sched.c:309
blk_mq_sched_dispatch_requests+0x88/0x120 block/blk-mq-sched.c:331
blk_mq_run_hw_queue+0x18a/0x230 block/blk-mq.c:2352
blk_mq_flush_plug_list+0xbd5/0xef0 block/blk-mq.c:2913
__blk_flush_plug+0x216/0x290 block/blk-core.c:1213
blk_finish_plug+0x48/0x70 block/blk-core.c:1240
ext4_do_writepages+0x1bec/0x2130 fs/ext4/inode.c:2786
ext4_writepages+0x159/0x2e0 fs/ext4/inode.c:2824
do_writepages+0x1d8/0x480 mm/page-writeback.c:2702
filemap_fdatawrite_wbc mm/filemap.c:397 [inline]
__filemap_fdatawrite_range mm/filemap.c:430 [inline]
file_write_and_wait_range+0x168/0x2f0 mm/filemap.c:787
ext4_sync_file+0x12e/0x6c0 fs/ext4/fsync.c:158
vfs_fsync_range+0x116/0x130 fs/sync.c:187
__do_sys_msync mm/msync.c:96 [inline]
__se_sys_msync+0x34d/0x510 mm/msync.c:32
__x64_sys_msync+0x43/0x50 mm/msync.c:32
x64_sys_call+0x112e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:27
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 19542 Comm: syz.4.14686 Not tainted 6.13.0-rc5-syzkaller-00161-g63676eefb7a0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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