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syzbot To: dakr@kernel.org, driver-core@lists.linux.dev, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 7a19f0cc94ad Merge branch 'for-next/core' into for-kernelci git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=17ba5fc9580000 kernel config: https://syzkaller.appspot.com/x/.config?x=6602d83d2f34eb80 dashboard link: https://syzkaller.appspot.com/bug?extid=a246ab421a728c78b4ad compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 userspace arch: arm64 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10b04a95580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+a246ab421a728c78b4ad@syzkaller.appspotmail.com block nbd0: reconnected socket ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz-executor796/5066 is trying to acquire lock: ffff800089aea6a0 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:316 [inline] ffff800089aea6a0 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4636 [inline] ffff800089aea6a0 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:4974 [inline] ffff800089aea6a0 (fs_reclaim){+.+.}-{0:0}, at: kmem_cache_alloc_node_noprof+0x64/0x604 mm/slub.c:5068 but task is already holding lock: ffff80008ae5fb20 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] ffff80008ae5fb20 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x24c/0x53c lib/kobject_uevent.c:410 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 (uevent_sock_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x164/0x1078 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] kobject_uevent_net_broadcast+0x24c/0x53c lib/kobject_uevent.c:410 kobject_uevent_env+0x518/0x944 lib/kobject_uevent.c:611 kobject_uevent+0x2c/0x3c lib/kobject_uevent.c:659 device_add+0x4d0/0x9e0 drivers/base/core.c:3742 device_register+0x28/0x38 drivers/base/core.c:3858 register_cpu+0x28c/0x57c drivers/base/cpu.c:431 arch_register_cpu+0x160/0x224 arch/arm64/kernel/smp.c:535 acpi_processor_hotadd_init drivers/acpi/acpi_processor.c:248 [inline] acpi_processor_get_info drivers/acpi/acpi_processor.c:370 [inline] acpi_processor_add+0x8f0/0x13f0 drivers/acpi/acpi_processor.c:441 acpi_scan_attach_handler drivers/acpi/scan.c:2325 [inline] acpi_bus_attach+0x398/0x778 drivers/acpi/scan.c:2374 acpi_dev_for_one_check+0xa0/0xb4 drivers/acpi/bus.c:1172 device_for_each_child+0xf4/0x184 drivers/base/core.c:4105 acpi_dev_for_each_child+0x98/0xe4 drivers/acpi/bus.c:1184 acpi_bus_attach+0x540/0x778 drivers/acpi/scan.c:2390 acpi_dev_for_one_check+0xa0/0xb4 drivers/acpi/bus.c:1172 device_for_each_child+0xf4/0x184 drivers/base/core.c:4105 acpi_dev_for_each_child+0x98/0xe4 drivers/acpi/bus.c:1184 acpi_bus_attach+0x540/0x778 drivers/acpi/scan.c:2390 acpi_bus_scan+0x104/0x310 drivers/acpi/scan.c:2740 acpi_scan_init+0x168/0x3cc drivers/acpi/scan.c:2866 acpi_init+0x15c/0x1f4 drivers/acpi/bus.c:1499 do_one_initcall+0x274/0x9f8 init/main.c:1362 do_initcall_level+0x12c/0x1c4 init/main.c:1424 do_initcalls+0x70/0xd0 init/main.c:1440 do_basic_setup+0x7c/0x90 init/main.c:1460 kernel_init_freeable+0x258/0x398 init/main.c:1675 kernel_init+0x28/0x1e0 init/main.c:1565 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #6 (cpu_hotplug_lock){++++}-{0:0}: percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read include/linux/percpu-rwsem.h:77 [inline] cpus_read_lock+0x54/0x1c8 kernel/cpu.c:490 static_key_slow_inc+0x1c/0x40 kernel/jump_label.c:190 sk_set_memalloc+0x6c/0xa0 net/core/sock.c:307 nbd_genl_reconnect_sock_cb+0x32c/0x72c drivers/block/nbd.c:1377 nbd_genl_foreach_sock+0x204/0x3c8 drivers/block/nbd.c:2152 nbd_genl_reconfigure+0x714/0x9e8 drivers/block/nbd.c:2477 genl_family_rcv_msg_doit+0x1e4/0x2d4 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x43c/0x620 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x238/0x414 net/netlink/af_netlink.c:2575 genl_rcv+0x38/0x50 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline] netlink_unicast+0x600/0x7f8 net/netlink/af_netlink.c:1364 netlink_sendmsg+0x648/0x948 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:800 [inline] __sock_sendmsg+0xc8/0x17c net/socket.c:815 __sys_sendto+0x250/0x328 net/socket.c:2281 __do_sys_sendto net/socket.c:2288 [inline] __se_sys_sendto net/socket.c:2284 [inline] __arm64_sys_sendto+0xec/0x10c net/socket.c:2284 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:796 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:815 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 -> #5 (&nsock->tx_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x164/0x1078 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 nbd_handle_cmd drivers/block/nbd.c:1143 [inline] nbd_queue_rq+0x1f4/0xbac drivers/block/nbd.c:1207 blk_mq_dispatch_rq_list+0x3d4/0x13a8 block/blk-mq.c:2130 __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+0xa48/0x10e8 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xa8/0x158 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x154/0x2e4 block/blk-mq.c:2545 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3479 worker_thread+0x798/0xbd0 kernel/workqueue.c:3560 kthread+0x304/0x3d4 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #4 (&cmd->lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x164/0x1078 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 nbd_queue_rq+0xb0/0xbac drivers/block/nbd.c:1199 blk_mq_dispatch_rq_list+0x3d4/0x13a8 block/blk-mq.c:2130 __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+0xa48/0x10e8 block/blk-mq-sched.c:307 blk_mq_sched_dispatch_requests+0xa8/0x158 block/blk-mq-sched.c:329 blk_mq_run_work_fn+0x154/0x2e4 block/blk-mq.c:2545 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0x91c/0x1250 kernel/workqueue.c:3479 worker_thread+0x798/0xbd0 kernel/workqueue.c:3560 kthread+0x304/0x3d4 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #3 (set->srcu){.+.+}-{0:0}: srcu_lock_sync include/linux/srcu.h:210 [inline] __synchronize_srcu+0xc8/0x268 kernel/rcu/srcutree.c:1462 synchronize_srcu+0x280/0x2e0 kernel/rcu/srcutree.c:-1 blk_mq_wait_quiesce_done+0x88/0xac block/blk-mq.c:284 blk_mq_quiesce_queue+0x70/0x8c block/blk-mq.c:304 elevator_switch+0x128/0x38c block/elevator.c:576 elevator_change+0x204/0x35c block/elevator.c:681 elevator_set_default+0x190/0x2b0 block/elevator.c:754 blk_register_queue+0x304/0x3dc block/blk-sysfs.c:992 __add_disk+0x5c8/0xbdc block/genhd.c:531 add_disk_fwnode+0xd4/0x340 block/genhd.c:600 device_add_disk+0x38/0x4c block/genhd.c:630 add_disk include/linux/blkdev.h:798 [inline] nbd_dev_add+0x594/0x884 drivers/block/nbd.c:2026 nbd_init+0x174/0x19c drivers/block/nbd.c:2743 do_one_initcall+0x274/0x9f8 init/main.c:1362 do_initcall_level+0x12c/0x1c4 init/main.c:1424 do_initcalls+0x70/0xd0 init/main.c:1440 do_basic_setup+0x7c/0x90 init/main.c:1460 kernel_init_freeable+0x258/0x398 init/main.c:1675 kernel_init+0x28/0x1e0 init/main.c:1565 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #2 (&q->elevator_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x164/0x1078 kernel/locking/mutex.c:821 mutex_lock_nested+0x24/0x30 kernel/locking/mutex.c:874 elevator_change+0x188/0x35c block/elevator.c:679 elevator_set_none+0xa8/0x13c block/elevator.c:769 blk_mq_elv_switch_none block/blk-mq.c:5113 [inline] __blk_mq_update_nr_hw_queues block/blk-mq.c:5158 [inline] blk_mq_update_nr_hw_queues+0x4c4/0x11e0 block/blk-mq.c:5223 nbd_start_device+0x15c/0xa44 drivers/block/nbd.c:1530 nbd_genl_connect+0xde4/0x12b0 drivers/block/nbd.c:2310 genl_family_rcv_msg_doit+0x1e4/0x2d4 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x43c/0x620 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x238/0x414 net/netlink/af_netlink.c:2575 genl_rcv+0x38/0x50 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1338 [inline] netlink_unicast+0x600/0x7f8 net/netlink/af_netlink.c:1364 netlink_sendmsg+0x648/0x948 net/netlink/af_netlink.c:1919 sock_sendmsg_nosec net/socket.c:800 [inline] __sock_sendmsg+0xc8/0x17c net/socket.c:815 __sys_sendto+0x250/0x328 net/socket.c:2281 __do_sys_sendto net/socket.c:2288 [inline] __se_sys_sendto net/socket.c:2284 [inline] __arm64_sys_sendto+0xec/0x10c net/socket.c:2284 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:796 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:815 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 -> #1 (&q->q_usage_counter(io)#33){++++}-{0:0}: blk_alloc_queue+0x488/0x590 block/blk-core.c:504 blk_mq_alloc_queue+0x148/0x284 block/blk-mq.c:4431 __blk_mq_alloc_disk+0x38/0x10c block/blk-mq.c:4478 nbd_dev_add+0x3d0/0x884 drivers/block/nbd.c:1996 nbd_init+0x174/0x19c drivers/block/nbd.c:2743 do_one_initcall+0x274/0x9f8 init/main.c:1362 do_initcall_level+0x12c/0x1c4 init/main.c:1424 do_initcalls+0x70/0xd0 init/main.c:1440 do_basic_setup+0x7c/0x90 init/main.c:1460 kernel_init_freeable+0x258/0x398 init/main.c:1675 kernel_init+0x28/0x1e0 init/main.c:1565 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:854 -> #0 (fs_reclaim){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1660/0x2b08 kernel/locking/lockdep.c:5288 lock_acquire+0x13c/0x320 kernel/locking/lockdep.c:5942 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x90/0x110 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] kmem_cache_alloc_node_noprof+0x64/0x604 mm/slub.c:5068 kmalloc_reserve+0xc4/0x214 net/core/skbuff.c:615 __alloc_skb+0x230/0x610 net/core/skbuff.c:715 alloc_skb include/linux/skbuff.h:1384 [inline] alloc_uevent_skb+0x78/0x1ec lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x2d4/0x53c lib/kobject_uevent.c:410 kobject_uevent_env+0x518/0x944 lib/kobject_uevent.c:611 kobject_synth_uevent+0x25c/0x730 lib/kobject_uevent.c:207 uevent_store+0x34/0x84 drivers/base/core.c:2847 dev_attr_store+0x6c/0x90 drivers/base/core.c:2509 sysfs_kf_write+0xe0/0x108 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x260/0x3b8 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x51c/0xa0c fs/read_write.c:687 ksys_write+0x12c/0x228 fs/read_write.c:739 __do_sys_write fs/read_write.c:750 [inline] __se_sys_write fs/read_write.c:747 [inline] __arm64_sys_write+0x84/0x98 fs/read_write.c:747 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:796 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:815 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 other info that might help us debug this: Chain exists of: fs_reclaim --> cpu_hotplug_lock --> uevent_sock_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(uevent_sock_mutex); lock(cpu_hotplug_lock); lock(uevent_sock_mutex); lock(fs_reclaim); *** DEADLOCK *** locks held by syz-executor796/5066: 5, last CPU#1: #0: ffff0000d2c57270 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x100/0x144 fs/file.c:1259 #1: ffff0000d0736460 (sb_writers#6){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2756 [inline] #1: ffff0000d0736460 (sb_writers#6){.+.+}-{0:0}, at: vfs_write+0x248/0xa0c fs/read_write.c:683 #2: ffff0000d1ef6c80 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1b0/0x3b8 fs/kernfs/file.c:336 #3: ffff0000c76cd2d8 (kn->active#4){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline] #3: ffff0000c76cd2d8 (kn->active#4){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x1f0/0x3b8 fs/kernfs/file.c:337 #4: ffff80008ae5fb20 (uevent_sock_mutex){+.+.}-{4:4}, at: uevent_net_broadcast_untagged lib/kobject_uevent.c:317 [inline] #4: ffff80008ae5fb20 (uevent_sock_mutex){+.+.}-{4:4}, at: kobject_uevent_net_broadcast+0x24c/0x53c lib/kobject_uevent.c:410 stack backtrace: CPU: 1 UID: 0 PID: 5066 Comm: syz-executor796 Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/23/2026 Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_circular_bug+0x328/0x330 kernel/locking/lockdep.c:2087 check_noncircular+0x158/0x174 kernel/locking/lockdep.c:2219 check_prev_add kernel/locking/lockdep.c:3209 [inline] check_prevs_add kernel/locking/lockdep.c:3328 [inline] validate_chain kernel/locking/lockdep.c:3952 [inline] __lock_acquire+0x1660/0x2b08 kernel/locking/lockdep.c:5288 lock_acquire+0x13c/0x320 kernel/locking/lockdep.c:5942 __fs_reclaim_acquire mm/page_alloc.c:4375 [inline] fs_reclaim_acquire+0x90/0x110 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] kmem_cache_alloc_node_noprof+0x64/0x604 mm/slub.c:5068 kmalloc_reserve+0xc4/0x214 net/core/skbuff.c:615 __alloc_skb+0x230/0x610 net/core/skbuff.c:715 alloc_skb include/linux/skbuff.h:1384 [inline] alloc_uevent_skb+0x78/0x1ec lib/kobject_uevent.c:289 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline] kobject_uevent_net_broadcast+0x2d4/0x53c lib/kobject_uevent.c:410 kobject_uevent_env+0x518/0x944 lib/kobject_uevent.c:611 kobject_synth_uevent+0x25c/0x730 lib/kobject_uevent.c:207 uevent_store+0x34/0x84 drivers/base/core.c:2847 dev_attr_store+0x6c/0x90 drivers/base/core.c:2509 sysfs_kf_write+0xe0/0x108 fs/sysfs/file.c:145 kernfs_fop_write_iter+0x260/0x3b8 fs/kernfs/file.c:345 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x51c/0xa0c fs/read_write.c:687 ksys_write+0x12c/0x228 fs/read_write.c:739 __do_sys_write fs/read_write.c:750 [inline] __se_sys_write fs/read_write.c:747 [inline] __arm64_sys_write+0x84/0x98 fs/read_write.c:747 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:796 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:815 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 --- This report is generated by a bot. 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