====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.1.1804/7534 is trying to acquire lock: ffff00000e164220 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x88/0xf0 fs/kernfs/inode.c:193 but task is already holding lock: ffff000014794ee8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x18/0x30 block/blk-mq.c:205 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#24){++++}-{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 loop_add+0x3b0/0x938 drivers/block/loop.c:2037 loop_init+0xd0/0x138 drivers/block/loop.c:2272 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 -> #1 (fs_reclaim){+.+.}-{0:0}: __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] slab_pre_alloc_hook mm/slub.c:4131 [inline] slab_alloc_node mm/slub.c:4209 [inline] kmem_cache_alloc_noprof+0x5c/0x3b8 mm/slub.c:4236 __kernfs_iattrs+0x10c/0x330 fs/kernfs/inode.c:36 kernfs_iattrs fs/kernfs/inode.c:61 [inline] __kernfs_setattr+0x4c/0x2a0 fs/kernfs/inode.c:74 kernfs_iop_setattr+0xc0/0xf4 fs/kernfs/inode.c:128 notify_change+0x3cc/0xba8 fs/attr.c:552 do_truncate+0x174/0x1bc fs/open.c:68 handle_truncate fs/namei.c:3508 [inline] do_open fs/namei.c:3891 [inline] path_openat+0x17c8/0x24b4 fs/namei.c:4046 do_filp_open+0x184/0x360 fs/namei.c:4073 do_sys_openat2+0xe0/0x160 fs/open.c:1435 do_sys_open fs/open.c:1450 [inline] __do_sys_openat fs/open.c:1466 [inline] __se_sys_openat fs/open.c:1461 [inline] __arm64_sys_openat+0x12c/0x1bc fs/open.c:1461 __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+0x40/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x50/0x1a0 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 -> #0 (&root->kernfs_iattr_rwsem){++++}-{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+0x1638/0x2380 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x310/0x38c kernel/locking/lockdep.c:5825 down_read+0xb4/0x314 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0x88/0xf0 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x1fc/0x374 fs/stat.c:213 vfs_getattr+0x40/0x54 fs/stat.c:262 loop_query_min_dio_size.isra.0+0xf8/0x1d0 drivers/block/loop.c:459 loop_assign_backing_file drivers/block/loop.c:512 [inline] loop_change_fd drivers/block/loop.c:590 [inline] lo_ioctl+0xde4/0x161c drivers/block/loop.c:1537 blkdev_ioctl+0x22c/0x7f4 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __arm64_sys_ioctl+0x124/0x1a4 fs/ioctl.c:584 __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+0x40/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x50/0x1a0 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 other info that might help us debug this: Chain exists of: &root->kernfs_iattr_rwsem --> fs_reclaim --> &q->q_usage_counter(io)#24 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#24); lock(fs_reclaim); lock(&q->q_usage_counter(io)#24); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz.1.1804/7534: #0: ffff000014a49400 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable+0x2c/0xbc drivers/block/loop.c:118 #1: ffff000014794ee8 (&q->q_usage_counter(io)#24){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x18/0x30 block/blk-mq.c:205 #2: ffff000014794f20 (&q->q_usage_counter(queue)#8){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x18/0x30 block/blk-mq.c:205 stack backtrace: CPU: 1 UID: 0 PID: 7534 Comm: syz.1.1804 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 down_read+0xb4/0x314 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0x88/0xf0 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x1fc/0x374 fs/stat.c:213 vfs_getattr+0x40/0x54 fs/stat.c:262 loop_query_min_dio_size.isra.0+0xf8/0x1d0 drivers/block/loop.c:459 loop_assign_backing_file drivers/block/loop.c:512 [inline] loop_change_fd drivers/block/loop.c:590 [inline] lo_ioctl+0xde4/0x161c drivers/block/loop.c:1537 blkdev_ioctl+0x22c/0x7f4 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl fs/ioctl.c:584 [inline] __arm64_sys_ioctl+0x124/0x1a4 fs/ioctl.c:584 __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+0x40/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x50/0x1a0 arch/arm64/kernel/entry-common.c:879 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:898 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596