[moderation] [block?] KCSAN: data-race in dd_insert_requests / ll_back_merge_fn (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 61387b8dcf1d Merge tag 'for-6.9/dm-vdo' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=147d6171180000
kernel config: https://syzkaller.appspot.com/x/.config?x=327f24e38a03e6ce
dashboard link: https://syzkaller.appspot.com/bug?extid=5831f74b165191ff3d98
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/95dd84609dcd/disk-61387b8d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3d4cbfef98ae/vmlinux-61387b8d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2b0da8a107a3/bzImage-61387b8d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5831f7...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dd_insert_requests / ll_back_merge_fn

write to 0xffff888101e8ceb8 of 8 bytes by task 31028 on cpu 0:
dd_insert_request block/mq-deadline.c:837 [inline]
dd_insert_requests+0x4b6/0x670 block/mq-deadline.c:878
blk_mq_dispatch_plug_list block/blk-mq.c:2772 [inline]
blk_mq_flush_plug_list+0x647/0xde0 block/blk-mq.c:2822
blk_add_rq_to_plug+0x102/0x3e0 block/blk-mq.c:1299
blk_mq_submit_bio+0x93d/0xdb0 block/blk-mq.c:3014
__submit_bio+0x11c/0x370 block/blk-core.c:619
__submit_bio_noacct_mq block/blk-core.c:698 [inline]
submit_bio_noacct_nocheck+0x502/0x6a0 block/blk-core.c:727
submit_bio_noacct+0x681/0x830 block/blk-core.c:837
submit_bio+0x218/0x230 block/blk-core.c:879
ext4_io_submit fs/ext4/page-io.c:378 [inline]
io_submit_add_bh fs/ext4/page-io.c:419 [inline]
ext4_bio_write_folio+0x6c0/0x9a0 fs/ext4/page-io.c:563
mpage_submit_folio fs/ext4/inode.c:1869 [inline]
mpage_map_and_submit_buffers fs/ext4/inode.c:2115 [inline]
mpage_map_and_submit_extent fs/ext4/inode.c:2254 [inline]
ext4_do_writepages+0x139f/0x2100 fs/ext4/inode.c:2679
ext4_writepages+0x15f/0x2f0 fs/ext4/inode.c:2768
do_writepages+0x1c6/0x340 mm/page-writeback.c:2553
filemap_fdatawrite_wbc+0xdb/0x100 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+0x2c1/0x660 fs/file_table.c:422
____fput+0x15/0x20 fs/file_table.c:450
task_work_run+0x13a/0x1a0 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x5fd/0x1740 kernel/exit.c:878
do_group_exit+0x102/0x150 kernel/exit.c:1027
get_signal+0xf53/0x10a0 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+0x94/0x130 kernel/entry/common.c:225
irqentry_exit+0x12/0x50 kernel/entry/common.c:328
exc_general_protection+0x33d/0x4d0 arch/x86/kernel/traps.c:644
asm_exc_general_protection+0x26/0x30 arch/x86/include/asm/idtentry.h:617

read to 0xffff888101e8ceb8 of 8 bytes by task 31037 on cpu 1:
req_set_nomerge block/blk.h:365 [inline]
ll_back_merge_fn+0x297/0x480 block/blk-merge.c:643
bio_attempt_back_merge+0x58/0x510 block/blk-merge.c:986
blk_attempt_bio_merge+0x44f/0x490 block/blk-merge.c:1072
blk_attempt_plug_merge+0xb5/0x100 block/blk-merge.c:1119
blk_mq_attempt_bio_merge block/blk-mq.c:2863 [inline]
blk_mq_submit_bio+0x5d9/0xdb0 block/blk-mq.c:2985
__submit_bio+0x11c/0x370 block/blk-core.c:619
__submit_bio_noacct_mq block/blk-core.c:698 [inline]
submit_bio_noacct_nocheck+0x502/0x6a0 block/blk-core.c:727
submit_bio_noacct+0x681/0x830 block/blk-core.c:837
submit_bio+0x218/0x230 block/blk-core.c:879
ext4_io_submit+0x8a/0xb0 fs/ext4/page-io.c:378
ext4_do_writepages+0xb3a/0x2100 fs/ext4/inode.c:2699
ext4_writepages+0x15f/0x2f0 fs/ext4/inode.c:2768
do_writepages+0x1c6/0x340 mm/page-writeback.c:2553
filemap_fdatawrite_wbc+0xdb/0x100 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+0x2c1/0x660 fs/file_table.c:422
____fput+0x15/0x20 fs/file_table.c:450
task_work_run+0x13a/0x1a0 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x5fd/0x1740 kernel/exit.c:878
do_group_exit+0x102/0x150 kernel/exit.c:1027
get_signal+0xf53/0x10a0 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+0x94/0x130 kernel/entry/common.c:225
irqentry_exit+0x12/0x50 kernel/entry/common.c:328
exc_general_protection+0x33d/0x4d0 arch/x86/kernel/traps.c:644
asm_exc_general_protection+0x26/0x30 arch/x86/include/asm/idtentry.h:617

value changed: 0x0000000000000000 -> 0xffff888102bb4440

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 31037 Comm: syz-executor.1 Not tainted 6.8.0-syzkaller-05562-g61387b8dcf1d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
==================================================================
syz-executor.1 (31037) used greatest stack depth: 9536 bytes left


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[syzbot]

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