====================================================== WARNING: possible circular locking dependency detected 6.14.0-syzkaller-10892-g4e82c87058f4 #0 Not tainted ------------------------------------------------------ syz.2.836/9693 is trying to acquire lock: ffff8880261e9958 (&q->elevator_lock){+.+.}-{4:4}, at: queue_requests_store+0x1c7/0x310 block/blk-sysfs.c:80 but task is already holding lock: ffff8880261e9428 (&q->q_usage_counter(io)#61){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#61){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x179/0x290 block/blk-mq.c:4349 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4396 nbd_dev_add+0x49d/0xbb0 drivers/block/nbd.c:1933 nbd_init+0x181/0x320 drivers/block/nbd.c:2670 do_one_initcall+0x120/0x6e0 init/main.c:1257 do_initcall_level init/main.c:1319 [inline] do_initcalls init/main.c:1335 [inline] do_basic_setup init/main.c:1354 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1567 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:3914 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:3928 might_alloc include/linux/sched/mm.h:318 [inline] xa_insert include/linux/xarray.h:783 [inline] blk_mq_init_hctx block/blk-mq.c:3924 [inline] blk_mq_alloc_and_init_hctx+0x503/0x11c0 block/blk-mq.c:4457 blk_mq_realloc_hw_ctxs+0x8f6/0xc00 block/blk-mq.c:4486 blk_mq_init_allocated_queue+0x3af/0x1230 block/blk-mq.c:4540 blk_mq_alloc_queue+0x1c2/0x290 block/blk-mq.c:4353 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4396 loop_add+0x496/0xb70 drivers/block/loop.c:2067 loop_init+0x164/0x270 drivers/block/loop.c:2302 do_one_initcall+0x120/0x6e0 init/main.c:1257 do_initcall_level init/main.c:1319 [inline] do_initcalls init/main.c:1335 [inline] do_basic_setup init/main.c:1354 [inline] kernel_init_freeable+0x5c2/0x900 init/main.c:1567 kernel_init+0x1c/0x2b0 init/main.c:1457 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (&q->elevator_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain kernel/locking/lockdep.c:3909 [inline] __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235 lock_acquire kernel/locking/lockdep.c:5866 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 __mutex_lock_common kernel/locking/mutex.c:587 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:732 queue_requests_store+0x1c7/0x310 block/blk-sysfs.c:80 queue_attr_store+0x270/0x310 block/blk-sysfs.c:799 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:591 [inline] vfs_write+0x5ba/0x1180 fs/read_write.c:684 ksys_write+0x12a/0x240 fs/read_write.c:736 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 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: &q->elevator_lock --> fs_reclaim --> &q->q_usage_counter(io)#61 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#61); lock(fs_reclaim); lock(&q->q_usage_counter(io)#61); lock(&q->elevator_lock); *** DEADLOCK *** 6 locks held by syz.2.836/9693: #0: ffff88803413e7f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1213 #1: ffff88803484e420 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x240 fs/read_write.c:736 #2: ffff88802525bc88 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x28f/0x510 fs/kernfs/file.c:325 #3: ffff888024a80d28 (kn->active#112){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x2b2/0x510 fs/kernfs/file.c:326 #4: ffff8880261e9428 (&q->q_usage_counter(io)#61){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215 #5: ffff8880261e9460 (&q->q_usage_counter(queue)#13){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:215 stack backtrace: CPU: 1 UID: 0 PID: 9693 Comm: syz.2.836 Not tainted 6.14.0-syzkaller-10892-g4e82c87058f4 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2079 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2211 check_prev_add kernel/locking/lockdep.c:3166 [inline] check_prevs_add kernel/locking/lockdep.c:3285 [inline] validate_chain kernel/locking/lockdep.c:3909 [inline] __lock_acquire+0x1173/0x1ba0 kernel/locking/lockdep.c:5235 lock_acquire kernel/locking/lockdep.c:5866 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5823 __mutex_lock_common kernel/locking/mutex.c:587 [inline] __mutex_lock+0x199/0xb90 kernel/locking/mutex.c:732 queue_requests_store+0x1c7/0x310 block/blk-sysfs.c:80 queue_attr_store+0x270/0x310 block/blk-sysfs.c:799 sysfs_kf_write+0x117/0x170 fs/sysfs/file.c:139 kernfs_fop_write_iter+0x351/0x510 fs/kernfs/file.c:334 new_sync_write fs/read_write.c:591 [inline] vfs_write+0x5ba/0x1180 fs/read_write.c:684 ksys_write+0x12a/0x240 fs/read_write.c:736 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x260 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fe7e158d169 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:00007fe7e23fb038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fe7e17a5fa0 RCX: 00007fe7e158d169 RDX: 0000000000000008 RSI: 0000200000000000 RDI: 0000000000000003 RBP: 00007fe7e23fb090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000000000 R14: 00007fe7e17a5fa0 R15: 00007fff4dbd8068