====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.4.1179/10760 is trying to acquire lock: ffffffff8e32eb28 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0xb4c/0x14c0 mm/percpu.c:1782 but task is already holding lock: ffff8880260b9e18 (&q->q_usage_counter(io)#53){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] ffff8880260b9e18 (&q->q_usage_counter(io)#53){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues+0x899/0x1200 block/blk-mq.c:5079 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#53){++++}-{0:0}: blk_alloc_queue+0x619/0x760 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4399 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4446 nbd_dev_add+0x492/0xbb0 drivers/block/nbd.c:1951 nbd_init+0x181/0x320 drivers/block/nbd.c:2688 do_one_initcall+0x120/0x6e0 init/main.c:1283 do_initcall_level init/main.c:1345 [inline] do_initcalls init/main.c:1361 [inline] do_basic_setup init/main.c:1380 [inline] kernel_init_freeable+0x5c2/0x910 init/main.c:1593 kernel_init+0x1c/0x2b0 init/main.c:1483 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:158 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:4269 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4283 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x162/0x610 mm/page_alloc.c:4951 __alloc_frozen_pages_noprof+0x18b/0x2470 mm/page_alloc.c:5172 __alloc_pages_noprof+0xb/0x1b0 mm/page_alloc.c:5217 __alloc_pages_node_noprof include/linux/gfp.h:284 [inline] alloc_pages_node_noprof include/linux/gfp.h:311 [inline] pcpu_alloc_pages mm/percpu-vm.c:95 [inline] pcpu_populate_chunk+0x110/0xb00 mm/percpu-vm.c:285 pcpu_alloc_noprof+0x86a/0x14c0 mm/percpu.c:1870 bpf_map_alloc_percpu+0x9a/0x4b0 kernel/bpf/syscall.c:560 prealloc_init kernel/bpf/hashtab.c:344 [inline] htab_map_alloc+0x10ca/0x1570 kernel/bpf/hashtab.c:569 map_create+0x659/0x27e0 kernel/bpf/syscall.c:1497 __sys_bpf+0x3d9d/0x4980 kernel/bpf/syscall.c:6116 __do_sys_bpf kernel/bpf/syscall.c:6244 [inline] __se_sys_bpf kernel/bpf/syscall.c:6242 [inline] __x64_sys_bpf+0x78/0xc0 kernel/bpf/syscall.c:6242 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (pcpu_alloc_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 pcpu_alloc_noprof+0xb4c/0x14c0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x2ff/0x770 lib/sbitmap.c:126 sbitmap_queue_init_node+0x40/0x4a0 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:546 [inline] blk_mq_init_tags+0x17f/0x320 block/blk-mq-tag.c:571 blk_mq_alloc_rq_map block/blk-mq.c:3534 [inline] blk_mq_alloc_map_and_rqs+0x222/0xeb0 block/blk-mq.c:4097 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4119 [inline] __blk_mq_alloc_map_and_rqs+0x128/0x1f0 block/blk-mq.c:4110 blk_mq_realloc_tag_set_tags block/blk-mq.c:4758 [inline] __blk_mq_update_nr_hw_queues+0xcc1/0x1200 block/blk-mq.c:5081 blk_mq_update_nr_hw_queues+0x3b/0x60 block/blk-mq.c:5133 nbd_start_device+0x1b0/0xd70 drivers/block/nbd.c:1486 nbd_start_device_ioctl drivers/block/nbd.c:1545 [inline] __nbd_ioctl drivers/block/nbd.c:1620 [inline] nbd_ioctl+0x219/0xda0 drivers/block/nbd.c:1660 blkdev_ioctl+0x274/0x6d0 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 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: pcpu_alloc_mutex --> fs_reclaim --> &q->q_usage_counter(io)#53 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#53); lock(fs_reclaim); lock(&q->q_usage_counter(io)#53); lock(pcpu_alloc_mutex); *** DEADLOCK *** 4 locks held by syz.4.1179/10760: #0: ffff8880260cf1c8 (&set->update_nr_hwq_lock){++++}-{4:4}, at: blk_mq_update_nr_hw_queues+0x27/0x60 block/blk-mq.c:5131 #1: ffff8880260cf0d8 (&set->tag_list_lock){+.+.}-{4:4}, at: blk_mq_update_nr_hw_queues+0x31/0x60 block/blk-mq.c:5132 #2: ffff8880260b9e18 (&q->q_usage_counter(io)#53){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] #2: ffff8880260b9e18 (&q->q_usage_counter(io)#53){++++}-{0:0}, at: __blk_mq_update_nr_hw_queues+0x899/0x1200 block/blk-mq.c:5079 #3: ffff8880260b9e50 (&q->q_usage_counter(queue)#37){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave block/blk-mq.c:205 [inline] #3: ffff8880260b9e50 (&q->q_usage_counter(queue)#37){+.+.}-{0:0}, at: __blk_mq_update_nr_hw_queues+0x899/0x1200 block/blk-mq.c:5079 stack backtrace: CPU: 1 UID: 0 PID: 10760 Comm: syz.4.1179 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 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:2043 check_noncircular+0x14c/0x170 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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x12a6/0x1ce0 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 pcpu_alloc_noprof+0xb4c/0x14c0 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x2ff/0x770 lib/sbitmap.c:126 sbitmap_queue_init_node+0x40/0x4a0 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:546 [inline] blk_mq_init_tags+0x17f/0x320 block/blk-mq-tag.c:571 blk_mq_alloc_rq_map block/blk-mq.c:3534 [inline] blk_mq_alloc_map_and_rqs+0x222/0xeb0 block/blk-mq.c:4097 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4119 [inline] __blk_mq_alloc_map_and_rqs+0x128/0x1f0 block/blk-mq.c:4110 blk_mq_realloc_tag_set_tags block/blk-mq.c:4758 [inline] __blk_mq_update_nr_hw_queues+0xcc1/0x1200 block/blk-mq.c:5081 blk_mq_update_nr_hw_queues+0x3b/0x60 block/blk-mq.c:5133 nbd_start_device+0x1b0/0xd70 drivers/block/nbd.c:1486 nbd_start_device_ioctl drivers/block/nbd.c:1545 [inline] __nbd_ioctl drivers/block/nbd.c:1620 [inline] nbd_ioctl+0x219/0xda0 drivers/block/nbd.c:1660 blkdev_ioctl+0x274/0x6d0 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0x4e0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fa6c818eec9 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:00007fa6c63ac038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fa6c83e6180 RCX: 00007fa6c818eec9 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000005 RBP: 00007fa6c8211f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa6c83e6218 R14: 00007fa6c83e6180 R15: 00007ffc2910d1b8 block nbd4: shutting down sockets