====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.10777/27159 is trying to acquire lock: ffff800087491ec0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:318 [inline] ffff800087491ec0 (fs_reclaim){+.+.}-{0:0}, at: prepare_alloc_pages+0x168/0x560 mm/page_alloc.c:4916 but task is already holding lock: ffff800087460008 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x8b4/0x11e8 mm/percpu.c:1782 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (pcpu_alloc_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x144/0xffc kernel/locking/mutex.c:760 _mutex_lock_killable+0x24/0x30 kernel/locking/mutex.c:828 pcpu_alloc_noprof+0x8b4/0x11e8 mm/percpu.c:1782 init_alloc_hint lib/sbitmap.c:16 [inline] sbitmap_init_node+0x224/0x718 lib/sbitmap.c:126 sbitmap_queue_init_node+0x3c/0x3d0 lib/sbitmap.c:454 bt_alloc block/blk-mq-tag.c:542 [inline] blk_mq_init_tags+0x100/0x230 block/blk-mq-tag.c:565 blk_mq_alloc_rq_map block/blk-mq.c:3542 [inline] blk_mq_alloc_map_and_rqs+0xa4/0xc54 block/blk-mq.c:4098 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4120 [inline] __blk_mq_alloc_map_and_rqs+0x100/0x1dc block/blk-mq.c:4111 blk_mq_realloc_tag_set_tags block/blk-mq.c:4759 [inline] __blk_mq_update_nr_hw_queues+0x7d8/0xd38 block/blk-mq.c:5072 blk_mq_update_nr_hw_queues+0x44/0x68 block/blk-mq.c:5124 nbd_start_device+0x128/0xa38 drivers/block/nbd.c:1478 nbd_genl_connect+0xcb4/0x14c4 drivers/block/nbd.c:2228 genl_family_rcv_msg_doit+0x1b8/0x280 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x3ec/0x5bc net/netlink/genetlink.c:1210 netlink_rcv_skb+0x19c/0x338 net/netlink/af_netlink.c:2552 genl_rcv+0x38/0x50 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline] netlink_unicast+0x424/0x700 net/netlink/af_netlink.c:1346 netlink_sendmsg+0x644/0xa54 net/netlink/af_netlink.c:1896 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg+0xc8/0x168 net/socket.c:729 ____sys_sendmsg+0x500/0x764 net/socket.c:2614 ___sys_sendmsg+0x11c/0x19c net/socket.c:2668 __sys_sendmsg+0x114/0x19c net/socket.c:2700 __compat_sys_sendmsg net/compat.c:346 [inline] __do_compat_sys_sendmsg net/compat.c:353 [inline] __se_compat_sys_sendmsg net/compat.c:350 [inline] __arm64_compat_sys_sendmsg+0x74/0xa4 net/compat.c:350 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc_compat+0x40/0x68 arch/arm64/kernel/syscall.c:157 el0_svc_compat+0x4c/0x184 arch/arm64/kernel/entry-common.c:1029 el0t_32_sync_handler+0x88/0xac arch/arm64/kernel/entry-common.c:1047 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:601 -> #1 (&q->q_usage_counter(io)#33){++++}-{0:0}: blk_alloc_queue+0x538/0x644 block/blk-core.c:461 blk_mq_alloc_queue+0x144/0x220 block/blk-mq.c:4400 __blk_mq_alloc_disk+0x20/0x1a4 block/blk-mq.c:4447 nbd_dev_add+0x3c0/0x9c0 drivers/block/nbd.c:1943 nbd_init+0xd4/0x1a8 drivers/block/nbd.c:2680 do_one_initcall+0x130/0x7f0 init/main.c:1269 do_initcall_level init/main.c:1331 [inline] do_initcalls init/main.c:1347 [inline] do_basic_setup init/main.c:1366 [inline] kernel_init_freeable+0x48c/0x70c init/main.c:1579 kernel_init+0x24/0x1dc init/main.c:1469 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860 -> #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 kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1638/0x2380 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x310/0x38c kernel/locking/lockdep.c:5825 __fs_reclaim_acquire mm/page_alloc.c:4234 [inline] fs_reclaim_acquire+0x138/0x160 mm/page_alloc.c:4248 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x168/0x560 mm/page_alloc.c:4916 __alloc_frozen_pages_noprof+0x144/0x1f20 mm/page_alloc.c:5137 __alloc_pages_noprof+0x14/0x114 mm/page_alloc.c:5182 __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+0xf0/0x90c mm/percpu-vm.c:285 pcpu_alloc_noprof+0x688/0x11e8 mm/percpu.c:1870 bpf_map_alloc_percpu+0xe4/0x5ac kernel/bpf/syscall.c:558 bpf_array_alloc_percpu kernel/bpf/arraymap.c:38 [inline] array_map_alloc+0x450/0x59c kernel/bpf/arraymap.c:152 map_create+0x3b8/0x1a68 kernel/bpf/syscall.c:1480 __sys_bpf+0xa30/0x29c8 kernel/bpf/syscall.c:6011 __do_sys_bpf kernel/bpf/syscall.c:6139 [inline] __se_sys_bpf kernel/bpf/syscall.c:6137 [inline] __arm64_sys_bpf+0x70/0xa4 kernel/bpf/syscall.c:6137 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc_compat+0x40/0x68 arch/arm64/kernel/syscall.c:157 el0_svc_compat+0x4c/0x184 arch/arm64/kernel/entry-common.c:1029 el0t_32_sync_handler+0x88/0xac arch/arm64/kernel/entry-common.c:1047 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:601 other info that might help us debug this: Chain exists of: fs_reclaim --> &q->q_usage_counter(io)#33 --> pcpu_alloc_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(pcpu_alloc_mutex); lock(&q->q_usage_counter(io)#33); lock(pcpu_alloc_mutex); lock(fs_reclaim); *** DEADLOCK *** 1 lock held by syz.3.10777/27159: #0: ffff800087460008 (pcpu_alloc_mutex){+.+.}-{4:4}, at: pcpu_alloc_noprof+0x8b4/0x11e8 mm/percpu.c:1782 stack backtrace: CPU: 1 UID: 0 PID: 27159 Comm: syz.3.10777 Not tainted syzkaller #0 PREEMPT Hardware name: linux,dummy-virt (DT) Call trace: show_stack+0x18/0x24 arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0xa4/0xf4 lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x28c/0x370 kernel/locking/lockdep.c:2043 check_noncircular+0x168/0x17c 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+0x1638/0x2380 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x310/0x38c kernel/locking/lockdep.c:5825 __fs_reclaim_acquire mm/page_alloc.c:4234 [inline] fs_reclaim_acquire+0x138/0x160 mm/page_alloc.c:4248 might_alloc include/linux/sched/mm.h:318 [inline] prepare_alloc_pages+0x168/0x560 mm/page_alloc.c:4916 __alloc_frozen_pages_noprof+0x144/0x1f20 mm/page_alloc.c:5137 __alloc_pages_noprof+0x14/0x114 mm/page_alloc.c:5182 __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+0xf0/0x90c mm/percpu-vm.c:285 pcpu_alloc_noprof+0x688/0x11e8 mm/percpu.c:1870 bpf_map_alloc_percpu+0xe4/0x5ac kernel/bpf/syscall.c:558 bpf_array_alloc_percpu kernel/bpf/arraymap.c:38 [inline] array_map_alloc+0x450/0x59c kernel/bpf/arraymap.c:152 map_create+0x3b8/0x1a68 kernel/bpf/syscall.c:1480 __sys_bpf+0xa30/0x29c8 kernel/bpf/syscall.c:6011 __do_sys_bpf kernel/bpf/syscall.c:6139 [inline] __se_sys_bpf kernel/bpf/syscall.c:6137 [inline] __arm64_sys_bpf+0x70/0xa4 kernel/bpf/syscall.c:6137 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132 do_el0_svc_compat+0x40/0x68 arch/arm64/kernel/syscall.c:157 el0_svc_compat+0x4c/0x184 arch/arm64/kernel/entry-common.c:1029 el0t_32_sync_handler+0x88/0xac arch/arm64/kernel/entry-common.c:1047 el0t_32_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:601