Hello,
syzbot found the following issue on:
HEAD commit: d724c6f85e80 Add linux-next specific files for 20251121
git tree: linux-next
console output:
https://syzkaller.appspot.com/x/log.txt?x=10bd3a12580000
kernel config:
https://syzkaller.appspot.com/x/.config?x=763fb984aa266726
dashboard link:
https://syzkaller.appspot.com/bug?extid=d64f92e22216675e2b0e
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image:
https://storage.googleapis.com/syzbot-assets/b2f349c65e3c/disk-d724c6f8.raw.xz
vmlinux:
https://storage.googleapis.com/syzbot-assets/aba40ae987ce/vmlinux-d724c6f8.xz
kernel image:
https://storage.googleapis.com/syzbot-assets/0b98fbfe576f/bzImage-d724c6f8.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by:
syzbot+d64f92...@syzkaller.appspotmail.com
loop6: detected capacity change from 0 to 524288000
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.3575/18878 is trying to acquire lock:
ffffffff8e448540 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline]
ffffffff8e448540 (fs_reclaim){+.+.}-{0:0}, at: mempool_alloc_noprof+0xa7/0x380 mm/mempool.c:559
but task is already holding lock:
ffff888025a40618 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:185 [inline]
ffff888025a40618 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:277 [inline]
ffff888025a40618 (set->srcu){.+.+}-{0:0}, at: blk_mq_dispatch_queue_requests+0x5f9/0x800 block/blk-mq.c:2897
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (set->srcu){.+.+}-{0:0}:
lock_sync+0xba/0x160 kernel/locking/lockdep.c:5916
srcu_lock_sync include/linux/srcu.h:197 [inline]
__synchronize_srcu+0x96/0x3a0 kernel/rcu/srcutree.c:1503
blk_throtl_init+0x298/0x410 block/blk-throttle.c:1324
tg_set_conf+0x1c6/0x4b0 block/blk-throttle.c:1359
cgroup_file_write+0x3a1/0x740 kernel/cgroup/cgroup.c:4312
kernfs_fop_write_iter+0x3af/0x540 fs/kernfs/file.c:352
new_sync_write fs/read_write.c:593 [inline]
vfs_write+0x5c9/0xb30 fs/read_write.c:686
ksys_write+0x145/0x250 fs/read_write.c:738
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&q->q_usage_counter(io)#17){++++}-{0:0}:
lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868
blk_alloc_queue+0x538/0x620 block/blk-core.c:461
blk_mq_alloc_queue block/blk-mq.c:4410 [inline]
__blk_mq_alloc_disk+0x15c/0x340 block/blk-mq.c:4457
loop_add+0x411/0xad0 drivers/block/loop.c:2206
loop_init+0xd9/0x170 drivers/block/loop.c:2441
do_one_initcall+0x1fb/0x870 init/main.c:1378
do_initcall_level+0x104/0x190 init/main.c:1440
do_initcalls+0x59/0xa0 init/main.c:1456
kernel_init_freeable+0x334/0x4b0 init/main.c:1688
kernel_init+0x1d/0x1d0 init/main.c:1578
ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
-> #0 (fs_reclaim){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2130 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4301 [inline]
fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4315
might_alloc include/linux/sched/mm.h:317 [inline]
mempool_alloc_noprof+0xa7/0x380 mm/mempool.c:559
bio_alloc_bioset+0x241/0x12a0 block/bio.c:559
__blkdev_direct_IO_async block/fops.c:338 [inline]
blkdev_direct_IO+0x9c0/0x17e0 block/fops.c:437
blkdev_read_iter+0x23d/0x440 block/fops.c:845
lo_submit_rw_aio+0x488/0x620 drivers/block/loop.c:-1
lo_rw_aio_nowait drivers/block/loop.c:513 [inline]
loop_queue_rq+0x6c5/0x8d0 drivers/block/loop.c:2036
__blk_mq_issue_directly block/blk-mq.c:2714 [inline]
blk_mq_request_issue_directly+0x3c1/0x710 block/blk-mq.c:2801
blk_mq_issue_direct+0x2a0/0x660 block/blk-mq.c:2822
blk_mq_dispatch_queue_requests+0x621/0x800 block/blk-mq.c:2897
blk_mq_flush_plug_list+0x432/0x550 block/blk-mq.c:2980
__blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
blk_finish_plug block/blk-core.c:1252 [inline]
__submit_bio+0x2d3/0x5a0 block/blk-core.c:651
__submit_bio_noacct_mq block/blk-core.c:724 [inline]
submit_bio_noacct_nocheck+0x2eb/0xa50 block/blk-core.c:755
submit_bh fs/buffer.c:2829 [inline]
block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
filemap_read_folio+0x117/0x380 mm/filemap.c:2496
do_read_cache_folio+0x358/0x590 mm/filemap.c:4096
read_mapping_folio include/linux/pagemap.h:1017 [inline]
read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
check_partition block/partitions/core.c:141 [inline]
blk_add_partitions block/partitions/core.c:589 [inline]
bdev_disk_changed+0x75f/0x14b0 block/partitions/core.c:693
loop_reread_partitions+0x5f/0xf0 drivers/block/loop.c:554
loop_configure+0xbd6/0xe50 drivers/block/loop.c:1248
lo_ioctl+0x806/0x1c50 drivers/block/loop.c:-1
blkdev_ioctl+0x60e/0x710 block/ioctl.c:707
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Chain exists of:
fs_reclaim --> &q->q_usage_counter(io)#17 --> set->srcu
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(set->srcu);
lock(&q->q_usage_counter(io)#17);
lock(set->srcu);
lock(fs_reclaim);
*** DEADLOCK ***
2 locks held by syz.2.3575/18878:
#0: ffff888025acb358 (&disk->open_mutex){+.+.}-{4:4}, at: loop_reread_partitions+0x46/0xf0 drivers/block/loop.c:553
#1: ffff888025a40618 (set->srcu){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:185 [inline]
#1: ffff888025a40618 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:277 [inline]
#1: ffff888025a40618 (set->srcu){.+.+}-{0:0}, at: blk_mq_dispatch_queue_requests+0x5f9/0x800 block/blk-mq.c:2897
stack backtrace:
CPU: 0 UID: 0 PID: 18878 Comm: syz.2.3575 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043
check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain+0xb9b/0x2130 kernel/locking/lockdep.c:3908
__lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868
__fs_reclaim_acquire mm/page_alloc.c:4301 [inline]
fs_reclaim_acquire+0x72/0x100 mm/page_alloc.c:4315
might_alloc include/linux/sched/mm.h:317 [inline]
mempool_alloc_noprof+0xa7/0x380 mm/mempool.c:559
bio_alloc_bioset+0x241/0x12a0 block/bio.c:559
__blkdev_direct_IO_async block/fops.c:338 [inline]
blkdev_direct_IO+0x9c0/0x17e0 block/fops.c:437
blkdev_read_iter+0x23d/0x440 block/fops.c:845
lo_submit_rw_aio+0x488/0x620 drivers/block/loop.c:-1
lo_rw_aio_nowait drivers/block/loop.c:513 [inline]
loop_queue_rq+0x6c5/0x8d0 drivers/block/loop.c:2036
__blk_mq_issue_directly block/blk-mq.c:2714 [inline]
blk_mq_request_issue_directly+0x3c1/0x710 block/blk-mq.c:2801
blk_mq_issue_direct+0x2a0/0x660 block/blk-mq.c:2822
blk_mq_dispatch_queue_requests+0x621/0x800 block/blk-mq.c:2897
blk_mq_flush_plug_list+0x432/0x550 block/blk-mq.c:2980
__blk_flush_plug+0x3d3/0x4b0 block/blk-core.c:1225
blk_finish_plug block/blk-core.c:1252 [inline]
__submit_bio+0x2d3/0x5a0 block/blk-core.c:651
__submit_bio_noacct_mq block/blk-core.c:724 [inline]
submit_bio_noacct_nocheck+0x2eb/0xa50 block/blk-core.c:755
submit_bh fs/buffer.c:2829 [inline]
block_read_full_folio+0x7b7/0x830 fs/buffer.c:2461
filemap_read_folio+0x117/0x380 mm/filemap.c:2496
do_read_cache_folio+0x358/0x590 mm/filemap.c:4096
read_mapping_folio include/linux/pagemap.h:1017 [inline]
read_part_sector+0xb6/0x2b0 block/partitions/core.c:722
adfspart_check_ICS+0xa4/0xa50 block/partitions/acorn.c:360
check_partition block/partitions/core.c:141 [inline]
blk_add_partitions block/partitions/core.c:589 [inline]
bdev_disk_changed+0x75f/0x14b0 block/partitions/core.c:693
loop_reread_partitions+0x5f/0xf0 drivers/block/loop.c:554
loop_configure+0xbd6/0xe50 drivers/block/loop.c:1248
lo_ioctl+0x806/0x1c50 drivers/block/loop.c:-1
blkdev_ioctl+0x60e/0x710 block/ioctl.c:707
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fad4518f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fad45f66038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fad453e5fa0 RCX: 00007fad4518f749
RDX: 0000200000001ac0 RSI: 0000000000004c0a RDI: 0000000000000007
RBP: 00007fad45213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fad453e6038 R14: 00007fad453e5fa0 R15: 00007fffcf7f94b8
</TASK>
---
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