====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.365/8324 is trying to acquire lock: ffff8880296cc5d0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:462 but task is already holding lock: ffff888062780418 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&type->i_mutex_dir_key#5){++++}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read+0x97/0x1f0 kernel/locking/rwsem.c:1537 inode_lock_shared include/linux/fs.h:885 [inline] lookup_slow+0x46/0x70 fs/namei.c:1824 walk_component+0x2d2/0x400 fs/namei.c:2129 lookup_last fs/namei.c:2630 [inline] path_lookupat+0x163/0x430 fs/namei.c:2654 filename_lookup+0x212/0x570 fs/namei.c:2683 kern_path+0x35/0x50 fs/namei.c:2816 is_same_device fs/btrfs/volumes.c:759 [inline] device_list_add+0xe2a/0x22a0 fs/btrfs/volumes.c:894 btrfs_scan_one_device+0x3ee/0x650 fs/btrfs/volumes.c:1493 btrfs_get_tree_super fs/btrfs/super.c:1856 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2080 [inline] btrfs_get_tree+0x433/0x1820 fs/btrfs/super.c:2114 vfs_get_tree+0x8f/0x2b0 fs/super.c:1815 do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808 do_mount fs/namespace.c:4136 [inline] __do_sys_mount fs/namespace.c:4347 [inline] __se_sys_mount+0x317/0x410 fs/namespace.c:4324 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (&fs_devs->device_list_mutex){+.+.}-{4:4}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/rtmutex_api.c:535 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:547 insert_dev_extents fs/btrfs/block-group.c:2754 [inline] btrfs_create_pending_block_groups+0x5f8/0x1780 fs/btrfs/block-group.c:2805 __btrfs_end_transaction+0x140/0x640 fs/btrfs/transaction.c:1071 flush_space+0x315/0xcd0 fs/btrfs/space-info.c:865 do_async_reclaim_data_space+0x11c/0x520 fs/btrfs/space-info.c:1394 btrfs_async_reclaim_data_space+0x41/0x90 fs/btrfs/space-info.c:1458 process_one_work kernel/workqueue.c:3236 [inline] process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (btrfs_trans_num_extwriters){++++}-{0:0}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 join_transaction+0x1a4/0xca0 fs/btrfs/transaction.c:321 start_transaction+0x6b6/0x1620 fs/btrfs/transaction.c:705 btrfs_rebuild_free_space_tree+0xad/0x760 fs/btrfs/free-space-tree.c:1339 btrfs_start_pre_rw_mount+0x128f/0x1bf0 fs/btrfs/disk-io.c:3075 open_ctree+0x293a/0x3a10 fs/btrfs/disk-io.c:3617 btrfs_fill_super fs/btrfs/super.c:980 [inline] btrfs_get_tree_super fs/btrfs/super.c:1943 [inline] btrfs_get_tree_subvol fs/btrfs/super.c:2080 [inline] btrfs_get_tree+0xf55/0x1820 fs/btrfs/super.c:2114 vfs_get_tree+0x8f/0x2b0 fs/super.c:1815 do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808 do_mount fs/namespace.c:4136 [inline] __do_sys_mount fs/namespace.c:4347 [inline] __se_sys_mount+0x317/0x410 fs/namespace.c:4324 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (btrfs_trans_num_writers){++++}-{0:0}: reacquire_held_locks+0x127/0x1d0 kernel/locking/lockdep.c:5385 __lock_release kernel/locking/lockdep.c:5574 [inline] lock_release+0x1b4/0x3e0 kernel/locking/lockdep.c:5889 percpu_up_read include/linux/percpu-rwsem.h:112 [inline] __sb_end_write include/linux/fs.h:1794 [inline] sb_end_intwrite+0x26/0x1c0 include/linux/fs.h:1911 __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1076 btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6258 inode_update_time fs/inode.c:2075 [inline] touch_atime+0x2f6/0x6d0 fs/inode.c:2148 file_accessed include/linux/fs.h:2664 [inline] btrfs_file_mmap_prepare+0xde/0x150 fs/btrfs/file.c:2050 vfs_mmap_prepare include/linux/fs.h:2295 [inline] call_mmap_prepare mm/vma.c:2585 [inline] __mmap_region mm/vma.c:2653 [inline] mmap_region+0xb49/0x20a0 mm/vma.c:2739 do_mmap+0xc23/0x10c0 mm/mmap.c:558 vm_mmap_pgoff+0x2a9/0x4d0 mm/util.c:580 ksys_mmap_pgoff+0x4e9/0x720 mm/mmap.c:604 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&mm->mmap_lock){++++}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:462 get_mmap_lock_carefully mm/mmap_lock.c:286 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:337 do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 user_access_begin arch/x86/include/asm/uaccess.h:-1 [inline] filldir+0x2a2/0x6c0 fs/readdir.c:290 dir_emit_dot include/linux/fs.h:3963 [inline] dir_emit_dots include/linux/fs.h:3974 [inline] offset_readdir+0x1e3/0x560 fs/libfs.c:569 iterate_dir+0x3a5/0x580 fs/readdir.c:108 __do_sys_getdents fs/readdir.c:326 [inline] __se_sys_getdents+0xe4/0x250 fs/readdir.c:312 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 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: &mm->mmap_lock --> &fs_devs->device_list_mutex --> &type->i_mutex_dir_key#5 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- rlock(&type->i_mutex_dir_key#5); lock(&fs_devs->device_list_mutex); lock(&type->i_mutex_dir_key#5); rlock(&mm->mmap_lock); *** DEADLOCK *** 2 locks held by syz.0.365/8324: #0: ffff88802b8f2f28 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x253/0x320 fs/file.c:1232 #1: ffff888062780418 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101 stack backtrace: CPU: 0 UID: 0 PID: 8324 Comm: syz.0.365 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 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+0xb9b/0x2140 kernel/locking/lockdep.c:3908 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868 down_read_killable+0x9d/0x220 kernel/locking/rwsem.c:1560 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:462 get_mmap_lock_carefully mm/mmap_lock.c:286 [inline] lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:337 do_user_addr_fault+0x331/0x1390 arch/x86/mm/fault.c:1359 handle_page_fault arch/x86/mm/fault.c:1476 [inline] exc_page_fault+0x76/0xf0 arch/x86/mm/fault.c:1532 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623 RIP: 0010:filldir+0x2a2/0x6c0 fs/readdir.c:294 Code: 8f ff 4c 89 ff 4c 89 e6 e8 4b 0a 8f ff 4d 39 e7 0f 82 7c 02 00 00 49 39 ef 0f 87 73 02 00 00 0f 01 cb 0f ae e8 48 8b 44 24 50 <49> 89 44 24 08 48 8b 4c 24 08 48 8b 44 24 58 48 89 01 48 8b 04 24 RSP: 0018:ffffc90005997c90 EFLAGS: 00050287 RAX: 0000000000000000 RBX: ffffc90005997e38 RCX: ffff888027168000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000018 RBP: 00007ffffffff000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000100 R11: ffffffff822f6410 R12: 0000000000000000 R13: ffffffff8b192060 R14: 0000000000000001 R15: 0000000000000018 dir_emit_dot include/linux/fs.h:3963 [inline] dir_emit_dots include/linux/fs.h:3974 [inline] offset_readdir+0x1e3/0x560 fs/libfs.c:569 iterate_dir+0x3a5/0x580 fs/readdir.c:108 __do_sys_getdents fs/readdir.c:326 [inline] __se_sys_getdents+0xe4/0x250 fs/readdir.c:312 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f606f70ec29 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:00007f606552c038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e RAX: ffffffffffffffda RBX: 00007f606f956180 RCX: 00007f606f70ec29 RDX: 0000000000000058 RSI: 0000000000000000 RDI: 0000000000000004 RBP: 00007f606f791e41 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f606f956218 R14: 00007f606f956180 R15: 00007ffe550171b8 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: ff 4c 89 ff decl -0x1(%rcx,%rcx,4) 4: 4c 89 e6 mov %r12,%rsi 7: e8 4b 0a 8f ff call 0xff8f0a57 c: 4d 39 e7 cmp %r12,%r15 f: 0f 82 7c 02 00 00 jb 0x291 15: 49 39 ef cmp %rbp,%r15 18: 0f 87 73 02 00 00 ja 0x291 1e: 0f 01 cb stac 21: 0f ae e8 lfence 24: 48 8b 44 24 50 mov 0x50(%rsp),%rax * 29: 49 89 44 24 08 mov %rax,0x8(%r12) <-- trapping instruction 2e: 48 8b 4c 24 08 mov 0x8(%rsp),%rcx 33: 48 8b 44 24 58 mov 0x58(%rsp),%rax 38: 48 89 01 mov %rax,(%rcx) 3b: 48 8b 04 24 mov (%rsp),%rax