====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.17/6095 is trying to acquire lock: ffff88801c68fa20 (&root->kernfs_iattr_rwsem){++++}-{4:4}, at: kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:193 but task is already holding lock: ffff88802657cca0 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:206 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&q->q_usage_counter(io)#26){++++}-{0:0}: blk_alloc_queue+0x610/0x750 block/blk-core.c:461 blk_mq_alloc_queue+0x172/0x280 block/blk-mq.c:4415 __blk_mq_alloc_disk+0x29/0x120 block/blk-mq.c:4462 loop_add+0x490/0xb70 drivers/block/loop.c:2050 loop_init+0x164/0x270 drivers/block/loop.c:2285 do_one_initcall+0x123/0x680 init/main.c:1378 do_initcall_level init/main.c:1440 [inline] do_initcalls init/main.c:1456 [inline] do_basic_setup init/main.c:1475 [inline] kernel_init_freeable+0x5c8/0x920 init/main.c:1688 kernel_init+0x1c/0x2b0 init/main.c:1578 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #1 (fs_reclaim){+.+.}-{0:0}: __fs_reclaim_acquire mm/page_alloc.c:4301 [inline] fs_reclaim_acquire+0x102/0x150 mm/page_alloc.c:4315 might_alloc include/linux/sched/mm.h:317 [inline] slab_pre_alloc_hook mm/slub.c:4904 [inline] slab_alloc_node mm/slub.c:5239 [inline] kmem_cache_alloc_noprof+0x5b/0x770 mm/slub.c:5270 __kernfs_iattrs+0x124/0x3e0 fs/kernfs/inode.c:36 kernfs_iattrs fs/kernfs/inode.c:61 [inline] __kernfs_setattr+0x4d/0x3c0 fs/kernfs/inode.c:74 kernfs_iop_setattr+0xda/0x120 fs/kernfs/inode.c:128 notify_change+0x6d2/0x1290 fs/attr.c:546 do_truncate+0x1d7/0x230 fs/open.c:68 handle_truncate fs/namei.c:4235 [inline] do_open fs/namei.c:4632 [inline] path_openat+0x2a1a/0x3140 fs/namei.c:4787 do_filp_open+0x20b/0x470 fs/namei.c:4814 do_sys_openat2+0x11f/0x280 fs/open.c:1430 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #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+0x1669/0x2890 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825 down_read+0x9b/0x460 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x2ac/0x430 fs/stat.c:213 vfs_getattr+0x4a/0x60 fs/stat.c:262 loop_query_min_dio_size.isra.0+0x117/0x250 drivers/block/loop.c:464 loop_assign_backing_file drivers/block/loop.c:517 [inline] loop_change_fd drivers/block/loop.c:597 [inline] lo_ioctl+0x1430/0x1cb0 drivers/block/loop.c:1546 blkdev_ioctl+0x5b0/0x6e0 block/ioctl.c:791 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/0xf80 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: &root->kernfs_iattr_rwsem --> fs_reclaim --> &q->q_usage_counter(io)#26 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&q->q_usage_counter(io)#26); lock(fs_reclaim); lock(&q->q_usage_counter(io)#26); rlock(&root->kernfs_iattr_rwsem); *** DEADLOCK *** 3 locks held by syz.0.17/6095: #0: ffff888102f96448 (&lo->lo_mutex){+.+.}-{4:4}, at: loop_global_lock_killable+0x30/0xb0 drivers/block/loop.c:118 #1: ffff88802657cca0 (&q->q_usage_counter(io)#26){++++}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:206 #2: ffff88802657ccd8 (&q->q_usage_counter(queue)#10){+.+.}-{0:0}, at: blk_mq_freeze_queue_nomemsave+0x15/0x20 block/blk-mq.c:206 stack backtrace: CPU: 2 UID: 0 PID: 6095 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x340 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 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+0x1669/0x2890 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825 down_read+0x9b/0x460 kernel/locking/rwsem.c:1537 kernfs_iop_getattr+0x9c/0xf0 fs/kernfs/inode.c:193 vfs_getattr_nosec+0x2ac/0x430 fs/stat.c:213 vfs_getattr+0x4a/0x60 fs/stat.c:262 loop_query_min_dio_size.isra.0+0x117/0x250 drivers/block/loop.c:464 loop_assign_backing_file drivers/block/loop.c:517 [inline] loop_change_fd drivers/block/loop.c:597 [inline] lo_ioctl+0x1430/0x1cb0 drivers/block/loop.c:1546 blkdev_ioctl+0x5b0/0x6e0 block/ioctl.c:791 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/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f99bd18f7c9 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:00007ffeb9539e28 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f99bd3e5fa0 RCX: 00007f99bd18f7c9 RDX: 0000000000000005 RSI: 0000000000004c06 RDI: 0000000000000003 RBP: 00007f99bd213f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f99bd3e5fa0 R14: 00007f99bd3e5fa0 R15: 0000000000000003