====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G W ------------------------------------------------------ kworker/1:1H/1385 is trying to acquire lock: ffff800087b74020 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:316 [inline] ffff800087b74020 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4636 [inline] ffff800087b74020 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4974 [inline] ffff800087b74020 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_node_noprof+0x6c/0x634 mm/slub.c:5578 but task is already holding lock: ffff000015adb480 (&new->lock){+.+.}-{4:4}, at: mtd_blktrans_work drivers/mtd/mtd_blkdevs.c:151 [inline] ffff000015adb480 (&new->lock){+.+.}-{4:4}, at: mtd_queue_rq+0x2a4/0x1694 drivers/mtd/mtd_blkdevs.c:179 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&new->lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5886 [inline] lock_acquire+0x3d0/0x44c kernel/locking/lockdep.c:5843 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x150/0x1530 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 mtd_blktrans_work drivers/mtd/mtd_blkdevs.c:151 [inline] mtd_queue_rq+0x2a4/0x1694 drivers/mtd/mtd_blkdevs.c:179 blk_mq_dispatch_rq_list+0x2e0/0x177c block/blk-mq.c:2117 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0x830/0xe60 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0x7c/0x114 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0xf0/0x278 block/blk-mq.c:2531 process_one_work+0x830/0x1c00 kernel/workqueue.c:3387 process_scheduled_works kernel/workqueue.c:3470 [inline] worker_thread+0x42c/0xc90 kernel/workqueue.c:3551 kthread+0x2ec/0x384 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #3 (set->srcu){.+.+}-{0:0}: lock_sync+0xf0/0x16c kernel/locking/lockdep.c:5934 srcu_lock_sync include/linux/srcu.h:210 [inline] __synchronize_srcu+0xa8/0x280 kernel/rcu/srcutree.c:1462 synchronize_srcu_expedited kernel/rcu/srcutree.c:1502 [inline] synchronize_srcu+0x168/0x7d0 kernel/rcu/srcutree.c:1558 blk_mq_wait_quiesce_done block/blk-mq.c:284 [inline] blk_mq_wait_quiesce_done block/blk-mq.c:281 [inline] blk_mq_quiesce_queue block/blk-mq.c:304 [inline] blk_mq_quiesce_queue+0xf4/0x160 block/blk-mq.c:299 elevator_switch+0x118/0x430 block/elevator.c:576 elevator_change+0x294/0x420 block/elevator.c:681 elevator_set_default+0x210/0x2b8 block/elevator.c:754 blk_register_queue+0x36c/0x500 block/blk-sysfs.c:992 __add_disk+0x510/0xb48 block/genhd.c:524 add_disk_fwnode+0x110/0x3e0 block/genhd.c:593 device_add_disk+0x14/0x20 block/genhd.c:623 add_disk include/linux/blkdev.h:798 [inline] nbd_dev_add+0x5f8/0x9b4 drivers/block/nbd.c:2026 nbd_init+0x190/0x1b0 drivers/block/nbd.c:2743 do_one_initcall+0x134/0xb20 init/main.c:1357 do_initcall_level init/main.c:1419 [inline] do_initcalls init/main.c:1435 [inline] do_basic_setup init/main.c:1455 [inline] kernel_init_freeable+0x5ec/0x670 init/main.c:1670 kernel_init+0x2c/0x14c init/main.c:1560 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #2 (&q->elevator_lock){+.+.}-{4:4}: lock_acquire kernel/locking/lockdep.c:5886 [inline] lock_acquire+0x3d0/0x44c kernel/locking/lockdep.c:5843 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x150/0x1530 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 elevator_change+0x188/0x420 block/elevator.c:679 elevator_set_none+0x90/0xec block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5102 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5147 [inline] blk_mq_update_nr_hw_queues+0x3c0/0x1020 block/blk-mq.c:5212 nbd_start_device+0x128/0xa28 drivers/block/nbd.c:1530 nbd_genl_connect+0xb50/0x1394 drivers/block/nbd.c:2310 genl_family_rcv_msg_doit+0x1c0/0x28c net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x3f8/0x60c net/netlink/genetlink.c:1209 netlink_rcv_skb+0x1ac/0x360 net/netlink/af_netlink.c:2556 genl_rcv+0x38/0x54 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x418/0x6e0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x638/0xa4c net/netlink/af_netlink.c:1900 sock_sendmsg_nosec net/socket.c:800 [inline] __sock_sendmsg+0xc8/0x1a4 net/socket.c:815 ____sys_sendmsg+0x52c/0x76c net/socket.c:2713 ___sys_sendmsg+0x124/0x1a4 net/socket.c:2767 __sys_sendmsg+0x10c/0x198 net/socket.c:2799 __compat_sys_sendmsg net/compat.c:345 [inline] __do_compat_sys_sendmsg net/compat.c:352 [inline] __se_compat_sys_sendmsg net/compat.c:349 [inline] __arm64_compat_sys_sendmsg+0x74/0xa4 net/compat.c:349 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x74/0x240 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:121 do_el0_svc_compat+0x40/0x58 arch/arm64/kernel/syscall.c:146 el0_svc_compat+0x54/0x264 arch/arm64/kernel/entry-common.c:909 el0t_32_sync_handler+0x88/0xac arch/arm64/kernel/entry-common.c:927 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:595 -> #1 (&q->q_usage_counter(io)#33){++++}-{0:0}: lock_acquire kernel/locking/lockdep.c:5886 [inline] lock_acquire+0x3d0/0x44c kernel/locking/lockdep.c:5843 blk_alloc_queue+0x4e0/0x640 block/blk-core.c:504 blk_mq_alloc_queue+0x148/0x224 block/blk-mq.c:4420 __blk_mq_alloc_disk+0x20/0x120 block/blk-mq.c:4467 nbd_dev_add+0x3d0/0x9b4 drivers/block/nbd.c:1996 nbd_init+0x190/0x1b0 drivers/block/nbd.c:2743 do_one_initcall+0x134/0xb20 init/main.c:1357 do_initcall_level init/main.c:1419 [inline] do_initcalls init/main.c:1435 [inline] do_basic_setup init/main.c:1455 [inline] kernel_init_freeable+0x5ec/0x670 init/main.c:1670 kernel_init+0x2c/0x14c init/main.c:1560 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #0 (fs_reclaim){+.+.}-{0:0}: check_prev_add+0x114/0xca0 kernel/locking/lockdep.c:3181 check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x13f4/0x1a5c kernel/locking/lockdep.c:5253 lock_acquire kernel/locking/lockdep.c:5886 [inline] lock_acquire+0x3d0/0x44c kernel/locking/lockdep.c:5843 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x130/0x158 mm/page_alloc.c:4389 might_alloc include/linux/sched/mm.h:316 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __kmalloc_cache_node_noprof+0x6c/0x634 mm/slub.c:5578 _kmalloc_node_noprof include/linux/slab.h:1196 [inline] __get_vm_area_node+0x118/0x2ec mm/vmalloc.c:3238 __vmalloc_node_range_noprof+0x198/0x1024 mm/vmalloc.c:4065 __vmalloc_node_noprof+0xe4/0x14c mm/vmalloc.c:4166 vmalloc_noprof+0x24/0x30 mm/vmalloc.c:4201 mtdblock_writesect+0x41c/0x5b8 drivers/mtd/mtdblock.c:242 do_blktrans_request drivers/mtd/mtd_blkdevs.c:88 [inline] mtd_blktrans_work drivers/mtd/mtd_blkdevs.c:152 [inline] mtd_queue_rq+0x744/0x1694 drivers/mtd/mtd_blkdevs.c:179 blk_mq_dispatch_rq_list+0x2e0/0x177c block/blk-mq.c:2117 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0x830/0xe60 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0x7c/0x114 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0xf0/0x278 block/blk-mq.c:2531 process_one_work+0x830/0x1c00 kernel/workqueue.c:3387 process_scheduled_works kernel/workqueue.c:3470 [inline] worker_thread+0x42c/0xc90 kernel/workqueue.c:3551 kthread+0x2ec/0x384 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 other info that might help us debug this: Chain exists of: fs_reclaim --> set->srcu --> &new->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&new->lock); lock(set->srcu); lock(&new->lock); lock(fs_reclaim); *** DEADLOCK *** locks held by kworker/1:1H/1385: 4, last CPU#1: #0: ffff00000f333d40 ((wq_completion)kblockd){+.+.}-{0:0}, at: process_one_work+0x12ec/0x1c00 kernel/workqueue.c:3362 #1: ffff80008f7e7c70 ((work_completion)(&(&hctx->run_work)->work)){+.+.}-{0:0}, at: process_one_work+0x780/0x1c00 kernel/workqueue.c:3361 #2: ffff0000128c0798 (set->srcu){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:304 [inline] #2: ffff0000128c0798 (set->srcu){.+.+}-{0:0}, at: blk_mq_run_work_fn+0xc8/0x278 block/blk-mq.c:2531 #3: ffff000015adb480 (&new->lock){+.+.}-{4:4}, at: mtd_blktrans_work drivers/mtd/mtd_blkdevs.c:151 [inline] #3: ffff000015adb480 (&new->lock){+.+.}-{4:4}, at: mtd_queue_rq+0x2a4/0x1694 drivers/mtd/mtd_blkdevs.c:179 stack backtrace: CPU: 1 UID: 0 PID: 1385 Comm: kworker/1:1H Tainted: G W syzkaller #0 PREEMPT Tainted: [W]=WARN Hardware name: linux,dummy-virt (DT) Workqueue: kblockd blk_mq_run_work_fn Call trace: show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x7c/0xb0 lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x23c/0x284 kernel/locking/lockdep.c:2059 check_noncircular+0x174/0x194 kernel/locking/lockdep.c:2191 check_prev_add+0x114/0xca0 kernel/locking/lockdep.c:3181 check_prevs_add kernel/locking/lockdep.c:3300 [inline] validate_chain kernel/locking/lockdep.c:3924 [inline] __lock_acquire+0x13f4/0x1a5c kernel/locking/lockdep.c:5253 lock_acquire kernel/locking/lockdep.c:5886 [inline] lock_acquire+0x3d0/0x44c kernel/locking/lockdep.c:5843 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x130/0x158 mm/page_alloc.c:4389 might_alloc include/linux/sched/mm.h:316 [inline] slab_pre_alloc_hook mm/slub.c:4636 [inline] slab_alloc_node mm/slub.c:4974 [inline] __kmalloc_cache_node_noprof+0x6c/0x634 mm/slub.c:5578 _kmalloc_node_noprof include/linux/slab.h:1196 [inline] __get_vm_area_node+0x118/0x2ec mm/vmalloc.c:3238 __vmalloc_node_range_noprof+0x198/0x1024 mm/vmalloc.c:4065 __vmalloc_node_noprof+0xe4/0x14c mm/vmalloc.c:4166 vmalloc_noprof+0x24/0x30 mm/vmalloc.c:4201 mtdblock_writesect+0x41c/0x5b8 drivers/mtd/mtdblock.c:242 do_blktrans_request drivers/mtd/mtd_blkdevs.c:88 [inline] mtd_blktrans_work drivers/mtd/mtd_blkdevs.c:152 [inline] mtd_queue_rq+0x744/0x1694 drivers/mtd/mtd_blkdevs.c:179 blk_mq_dispatch_rq_list+0x2e0/0x177c block/blk-mq.c:2117 __blk_mq_do_dispatch_sched block/blk-mq-sched.c:168 [inline] blk_mq_do_dispatch_sched block/blk-mq-sched.c:182 [inline] __blk_mq_sched_dispatch_requests+0x830/0xe60 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0x7c/0x114 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0xf0/0x278 block/blk-mq.c:2531 process_one_work+0x830/0x1c00 kernel/workqueue.c:3387 process_scheduled_works kernel/workqueue.c:3470 [inline] worker_thread+0x42c/0xc90 kernel/workqueue.c:3551 kthread+0x2ec/0x384 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854