====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.1730/9400 is trying to acquire lock: ffff0000db0e3d48 (&mm->mmap_lock){++++}-{3:3}, at: __might_fault+0x9c/0x124 mm/memory.c:5849 but task is already holding lock: ffff0000c09208e0 (&type->i_mutex_dir_key#2){++++}-{3:3}, at: iterate_dir+0x108/0x4cc fs/readdir.c:55 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&type->i_mutex_dir_key#2){++++}-{3:3}: down_read+0x64/0x300 kernel/locking/rwsem.c:1520 inode_lock_shared include/linux/fs.h:768 [inline] lookup_slow+0x4c/0x80 fs/namei.c:1714 walk_component+0x270/0x364 fs/namei.c:2006 lookup_last fs/namei.c:2463 [inline] path_lookupat+0x13c/0x3d0 fs/namei.c:2487 filename_lookup+0x1c4/0x480 fs/namei.c:2516 kern_path+0x48/0x6c fs/namei.c:2614 is_same_device fs/btrfs/volumes.c:695 [inline] device_list_add+0x129c/0x1c84 fs/btrfs/volumes.c:928 btrfs_scan_one_device+0x368/0x57c fs/btrfs/volumes.c:1461 btrfs_mount_root+0x45c/0x7d0 fs/btrfs/super.c:1796 legacy_get_tree+0xd4/0x16c fs/fs_context.c:632 vfs_get_tree+0x90/0x274 fs/super.c:1573 fc_mount fs/namespace.c:1048 [inline] vfs_kern_mount+0xdc/0x178 fs/namespace.c:1078 btrfs_mount+0x2dc/0x974 fs/btrfs/super.c:1894 legacy_get_tree+0xd4/0x16c fs/fs_context.c:632 vfs_get_tree+0x90/0x274 fs/super.c:1573 do_new_mount+0x228/0x810 fs/namespace.c:3078 path_mount+0x5bc/0xe80 fs/namespace.c:3408 do_mount fs/namespace.c:3421 [inline] __do_sys_mount fs/namespace.c:3629 [inline] __se_sys_mount fs/namespace.c:3606 [inline] __arm64_sys_mount+0x49c/0x59c fs/namespace.c:3606 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #4 (&fs_devs->device_list_mutex){+.+.}-{3:3}: __mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 btrfs_run_dev_stats+0xf8/0xdc8 fs/btrfs/volumes.c:8071 commit_cowonly_roots+0x170/0x71c fs/btrfs/transaction.c:1298 btrfs_commit_transaction+0x10e8/0x2884 fs/btrfs/transaction.c:2444 btrfs_commit_super+0xac/0xc8 fs/btrfs/disk-io.c:4519 close_ctree+0x400/0xa94 fs/btrfs/disk-io.c:4726 btrfs_put_super+0x70/0x80 fs/btrfs/super.c:397 generic_shutdown_super+0x130/0x324 fs/super.c:501 kill_anon_super+0x4c/0x80 fs/super.c:1128 btrfs_kill_super+0x40/0x58 fs/btrfs/super.c:2448 deactivate_locked_super+0xac/0x120 fs/super.c:332 deactivate_super+0xe4/0x104 fs/super.c:363 cleanup_mnt+0x390/0x418 fs/namespace.c:1191 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198 task_work_run+0x1ec/0x278 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x1fa0/0x2aa4 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #3 (&fs_info->reloc_mutex){+.+.}-{3:3}: __mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 btrfs_commit_transaction+0xf98/0x2884 fs/btrfs/transaction.c:2384 btrfs_commit_super+0xac/0xc8 fs/btrfs/disk-io.c:4519 close_ctree+0x400/0xa94 fs/btrfs/disk-io.c:4726 btrfs_put_super+0x70/0x80 fs/btrfs/super.c:397 generic_shutdown_super+0x130/0x324 fs/super.c:501 kill_anon_super+0x4c/0x80 fs/super.c:1128 btrfs_kill_super+0x40/0x58 fs/btrfs/super.c:2448 deactivate_locked_super+0xac/0x120 fs/super.c:332 deactivate_super+0xe4/0x104 fs/super.c:363 cleanup_mnt+0x390/0x418 fs/namespace.c:1191 __cleanup_mnt+0x20/0x30 fs/namespace.c:1198 task_work_run+0x1ec/0x278 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x1fa0/0x2aa4 arch/arm64/kernel/signal.c:1151 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline] exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline] el0_svc+0x98/0x128 arch/arm64/kernel/entry-common.c:638 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #2 (btrfs_trans_unblocked){++++}-{0:0}: wait_current_trans+0x220/0x49c fs/btrfs/transaction.c:517 start_transaction+0x87c/0x1050 fs/btrfs/transaction.c:670 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781 btrfs_ioctl_qgroup_assign+0x10c/0x270 fs/btrfs/ioctl.c:4666 btrfs_ioctl+0x5b4/0xb38 fs/btrfs/ioctl.c:5615 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #1 (sb_internal#3){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1891 [inline] sb_start_intwrite include/linux/fs.h:2013 [inline] start_transaction+0x5c4/0x1050 fs/btrfs/transaction.c:662 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:781 btrfs_dirty_inode+0xb4/0x1c0 fs/btrfs/inode.c:6285 btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6327 inode_update_time fs/inode.c:1958 [inline] touch_atime+0x368/0x7dc fs/inode.c:2031 file_accessed include/linux/fs.h:2600 [inline] btrfs_file_mmap+0xb0/0x11c fs/btrfs/file.c:2053 call_mmap include/linux/fs.h:2270 [inline] mmap_file+0x6c/0xc8 mm/util.c:1109 __mmap_region mm/mmap.c:2772 [inline] mmap_region+0xcec/0x1900 mm/mmap.c:2916 do_mmap+0x9cc/0x1138 mm/mmap.c:1436 vm_mmap_pgoff+0x190/0x294 mm/util.c:520 ksys_mmap_pgoff+0x3b8/0x5a0 mm/mmap.c:1482 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline] __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline] __arm64_sys_mmap+0xf8/0x110 arch/arm64/kernel/sys.c:21 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 -> #0 (&mm->mmap_lock){++++}-{3:3}: check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049 lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662 __might_fault+0xc4/0x124 mm/memory.c:5850 filldir64+0x2cc/0x8fc fs/readdir.c:335 dir_emit_dot include/linux/fs.h:3698 [inline] dir_emit_dots include/linux/fs.h:3709 [inline] dcache_readdir+0x140/0x62c fs/libfs.c:197 iterate_dir+0x1f0/0x4cc fs/readdir.c:-1 __do_sys_getdents64 fs/readdir.c:369 [inline] __se_sys_getdents64 fs/readdir.c:354 [inline] __arm64_sys_getdents64+0x11c/0x320 fs/readdir.c:354 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585 other info that might help us debug this: Chain exists of: &mm->mmap_lock --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&type->i_mutex_dir_key#2); lock(&fs_devs->device_list_mutex); lock(&type->i_mutex_dir_key#2); lock(&mm->mmap_lock); *** DEADLOCK *** 2 locks held by syz.0.1730/9400: #0: ffff0000f4720368 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x114/0x16c fs/file.c:1038 #1: ffff0000c09208e0 (&type->i_mutex_dir_key#2){++++}-{3:3}, at: iterate_dir+0x108/0x4cc fs/readdir.c:55 stack backtrace: CPU: 1 PID: 9400 Comm: syz.0.1730 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call trace: dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165 __dump_stack+0x30/0x40 lib/dump_stack.c:88 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106 dump_stack+0x1c/0x5c lib/dump_stack.c:113 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170 check_prev_add kernel/locking/lockdep.c:3090 [inline] check_prevs_add kernel/locking/lockdep.c:3209 [inline] validate_chain kernel/locking/lockdep.c:3825 [inline] __lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049 lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662 __might_fault+0xc4/0x124 mm/memory.c:5850 filldir64+0x2cc/0x8fc fs/readdir.c:335 dir_emit_dot include/linux/fs.h:3698 [inline] dir_emit_dots include/linux/fs.h:3709 [inline] dcache_readdir+0x140/0x62c fs/libfs.c:197 iterate_dir+0x1f0/0x4cc fs/readdir.c:-1 __do_sys_getdents64 fs/readdir.c:369 [inline] __se_sys_getdents64 fs/readdir.c:354 [inline] __arm64_sys_getdents64+0x11c/0x320 fs/readdir.c:354 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585