====================================================== WARNING: possible circular locking dependency detected 6.1.140-syzkaller #0 Not tainted ------------------------------------------------------ udevd/4400 is trying to acquire lock: ffff0000c62fb748 (&mm->mmap_lock){++++}-{3:3}, at: __might_fault+0x9c/0x124 mm/memory.c:5851 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+0x64/0x304 kernel/locking/rwsem.c:1520 inode_lock_shared include/linux/fs.h:768 [inline] lookup_slow+0x4c/0x80 fs/namei.c:1706 walk_component+0x270/0x364 fs/namei.c:1998 lookup_last fs/namei.c:2455 [inline] path_lookupat+0x13c/0x3d0 fs/namei.c:2479 filename_lookup+0x190/0x42c fs/namei.c:2508 kern_path+0x48/0x6c fs/namei.c:2606 is_same_device fs/btrfs/volumes.c:695 [inline] device_list_add+0x1208/0x1be0 fs/btrfs/volumes.c:928 btrfs_scan_one_device+0x364/0x570 fs/btrfs/volumes.c:1461 btrfs_mount_root+0x404/0x780 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:1043 [inline] vfs_kern_mount+0xdc/0x178 fs/namespace.c:1073 btrfs_mount+0x2a0/0x8dc 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:3058 path_mount+0x5b4/0xe78 fs/namespace.c:3388 do_mount fs/namespace.c:3401 [inline] __do_sys_mount fs/namespace.c:3609 [inline] __se_sys_mount fs/namespace.c:3586 [inline] __arm64_sys_mount+0x49c/0x584 fs/namespace.c:3586 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 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+0x190/0x1f38 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+0xf0/0xd00 fs/btrfs/volumes.c:8058 commit_cowonly_roots+0x16c/0x714 fs/btrfs/transaction.c:1297 btrfs_commit_transaction+0x10bc/0x29f0 fs/btrfs/transaction.c:2427 btrfs_commit_super+0xac/0xc8 fs/btrfs/disk-io.c:4542 close_ctree+0x39c/0xa64 fs/btrfs/disk-io.c:4728 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/0x124 fs/super.c:332 deactivate_super+0xe8/0x108 fs/super.c:363 cleanup_mnt+0x37c/0x404 fs/namespace.c:1186 __cleanup_mnt+0x20/0x30 fs/namespace.c:1193 task_work_run+0x1ec/0x270 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x1f70/0x2b0c arch/arm64/kernel/signal.c:1137 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+0x98/0x138 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+0x190/0x1f38 kernel/locking/mutex.c:603 __mutex_lock kernel/locking/mutex.c:747 [inline] mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799 btrfs_record_root_in_trans fs/btrfs/transaction.c:488 [inline] start_transaction+0x434/0x104c fs/btrfs/transaction.c:730 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:780 cow_file_range_inline+0x208/0x78c fs/btrfs/inode.c:421 cow_file_range+0x2d8/0xbac fs/btrfs/inode.c:1219 btrfs_run_delalloc_range+0x310/0xf18 fs/btrfs/inode.c:2233 writepage_delalloc+0x110/0x2dc fs/btrfs/extent_io.c:1972 __extent_writepage+0x528/0xc20 fs/btrfs/extent_io.c:2276 extent_write_cache_pages fs/btrfs/extent_io.c:3191 [inline] extent_writepages+0x928/0x102c fs/btrfs/extent_io.c:3313 btrfs_writepages+0x28/0x38 fs/btrfs/inode.c:8300 do_writepages+0x2c0/0x4fc mm/page-writeback.c:2491 filemap_fdatawrite_wbc+0x124/0x174 mm/filemap.c:388 __filemap_fdatawrite_range mm/filemap.c:421 [inline] filemap_fdatawrite_range+0xbc/0x10c mm/filemap.c:439 btrfs_fdatawrite_range fs/btrfs/file.c:3880 [inline] start_ordered_ops+0xe8/0x224 fs/btrfs/file.c:1742 btrfs_sync_file+0x398/0xf44 fs/btrfs/file.c:1825 vfs_fsync_range+0x168/0x188 fs/sync.c:188 generic_write_sync include/linux/fs.h:2962 [inline] btrfs_do_write_iter+0xafc/0x1154 fs/btrfs/file.c:1691 btrfs_file_write_iter+0x2c/0x3c fs/btrfs/file.c:1705 do_iter_readv_writev fs/read_write.c:-1 [inline] do_iter_write+0x530/0x91c fs/read_write.c:861 vfs_writev fs/read_write.c:934 [inline] do_pwritev+0x1c8/0x2fc fs/read_write.c:1031 __do_sys_pwritev2 fs/read_write.c:1090 [inline] __se_sys_pwritev2 fs/read_write.c:1081 [inline] __arm64_sys_pwritev2+0xd4/0x108 fs/read_write.c:1081 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 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 -> #2 (btrfs_trans_num_extwriters){++++}-{0:0}: join_transaction+0x180/0xb6c fs/btrfs/transaction.c:303 start_transaction+0x854/0x104c fs/btrfs/transaction.c:667 btrfs_join_transaction+0x30/0x40 fs/btrfs/transaction.c:780 btrfs_commit_super+0x8c/0xc8 fs/btrfs/disk-io.c:4539 close_ctree+0x39c/0xa64 fs/btrfs/disk-io.c:4728 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/0x124 fs/super.c:332 deactivate_super+0xe8/0x108 fs/super.c:363 cleanup_mnt+0x37c/0x404 fs/namespace.c:1186 __cleanup_mnt+0x20/0x30 fs/namespace.c:1193 task_work_run+0x1ec/0x270 kernel/task_work.c:203 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] do_notify_resume+0x1f70/0x2b0c arch/arm64/kernel/signal.c:1137 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+0x98/0x138 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 -> #1 (btrfs_trans_num_writers){++++}-{0:0}: __lock_release kernel/locking/lockdep.c:5376 [inline] lock_release+0x308/0x910 kernel/locking/lockdep.c:5682 percpu_up_read include/linux/percpu-rwsem.h:99 [inline] __sb_end_write include/linux/fs.h:1886 [inline] sb_end_intwrite+0x54/0x360 include/linux/fs.h:1942 __btrfs_end_transaction+0x1f4/0x5fc fs/btrfs/transaction.c:1017 btrfs_end_transaction+0x24/0x34 fs/btrfs/transaction.c:1051 btrfs_dirty_inode+0x16c/0x1c0 fs/btrfs/inode.c:6288 btrfs_update_time+0x170/0x18c fs/btrfs/inode.c:6316 inode_update_time fs/inode.c:1958 [inline] touch_atime+0x364/0x7d0 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:2760 [inline] mmap_region+0xcc8/0x1860 mm/mmap.c:2904 do_mmap+0x978/0x10dc mm/mmap.c:1424 vm_mmap_pgoff+0x184/0x284 mm/util.c:520 ksys_mmap_pgoff+0x3b8/0x5a0 mm/mmap.c:1470 __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+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 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+0x293c/0x6544 kernel/locking/lockdep.c:5049 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662 __might_fault+0xc4/0x124 mm/memory.c:5852 filldir64+0x2cc/0x8fc fs/readdir.c:335 dir_emit_dot include/linux/fs.h:3699 [inline] dir_emit_dots include/linux/fs.h:3710 [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/0x318 fs/readdir.c:354 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 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 udevd/4400: #0: ffff0000c9a52368 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x114/0x16c fs/file.c:1040 #1: ffff0000c09208e0 (&type->i_mutex_dir_key#2){++++}-{3:3}, at: iterate_dir+0x108/0x4cc fs/readdir.c:55 stack backtrace: CPU: 1 PID: 4400 Comm: udevd Not tainted 6.1.140-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call trace: dump_backtrace+0x1c8/0x1f4 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+0xf8/0x160 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+0x240/0x2d4 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+0x293c/0x6544 kernel/locking/lockdep.c:5049 lock_acquire+0x20c/0x644 kernel/locking/lockdep.c:5662 __might_fault+0xc4/0x124 mm/memory.c:5852 filldir64+0x2cc/0x8fc fs/readdir.c:335 dir_emit_dot include/linux/fs.h:3699 [inline] dir_emit_dots include/linux/fs.h:3710 [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/0x318 fs/readdir.c:354 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline] invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204 el0_svc+0x58/0x138 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