syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.5.751/18688 is trying to acquire lock:
ffff88803f839db0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601

but task is already holding lock:
ffff88803b001c78 (&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}:
       down_read+0x97/0x200 kernel/locking/rwsem.c:1537
       inode_lock_shared include/linux/fs.h:1043 [inline]
       lookup_slow+0x46/0x70 fs/namei.c:1932
       walk_component fs/namei.c:2279 [inline]
       lookup_last fs/namei.c:2786 [inline]
       path_lookupat+0x3f5/0x8c0 fs/namei.c:2810
       filename_lookup+0x256/0x5d0 fs/namei.c:2839
       kern_path+0x3d/0x150 fs/namei.c:3046
       is_same_device fs/btrfs/volumes.c:763 [inline]
       device_list_add+0xfd1/0x2280 fs/btrfs/volumes.c:897
       btrfs_scan_one_device+0x3ef/0x680 fs/btrfs/volumes.c:1498
       btrfs_get_tree_super fs/btrfs/super.c:1858 [inline]
       btrfs_get_tree_subvol fs/btrfs/super.c:2087 [inline]
       btrfs_get_tree+0x4ab/0x1930 fs/btrfs/super.c:2121
       vfs_get_tree+0x92/0x2a0 fs/super.c:1754
       fc_mount fs/namespace.c:1193 [inline]
       do_new_mount_fc fs/namespace.c:3763 [inline]
       do_new_mount+0x341/0xd30 fs/namespace.c:3839
       do_mount fs/namespace.c:4172 [inline]
       __do_sys_mount fs/namespace.c:4361 [inline]
       __se_sys_mount+0x31d/0x420 fs/namespace.c:4338
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (&fs_devs->device_list_mutex){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
       mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
       insert_dev_extents fs/btrfs/block-group.c:2838 [inline]
       btrfs_create_pending_block_groups+0x77b/0x1b40 fs/btrfs/block-group.c:2889
       __btrfs_end_transaction+0x140/0x640 fs/btrfs/transaction.c:1080
       flush_space+0x35e/0xd80 fs/btrfs/space-info.c:900
       do_async_reclaim_metadata_space+0x411/0x970 fs/btrfs/space-info.c:1187
       btrfs_async_reclaim_metadata_space+0x89/0xe0 fs/btrfs/space-info.c:1254
       process_one_work kernel/workqueue.c:3288 [inline]
       process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3371
       worker_thread+0xa53/0xfc0 kernel/workqueue.c:3452
       kthread+0x388/0x470 kernel/kthread.c:436
       ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (btrfs_trans_num_extwriters){++++}-{0:0}:
       join_transaction+0x1a4/0xc90 fs/btrfs/transaction.c:323
       start_transaction+0x6b9/0x1650 fs/btrfs/transaction.c:708
       btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6443
       touch_atime+0x2f8/0x6b0 fs/inode.c:2271
       file_accessed include/linux/fs.h:2263 [inline]
       filemap_read+0x105c/0x1240 mm/filemap.c:2877
       __kernel_read+0x50d/0x9c0 fs/read_write.c:532
       integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
       ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:480 [inline]
       ima_calc_file_shash security/integrity/ima/ima_crypto.c:511 [inline]
       ima_calc_file_hash+0x12cf/0x1800 security/integrity/ima/ima_crypto.c:568
       ima_collect_measurement+0x491/0x930 security/integrity/ima/ima_api.c:295
       process_measurement+0x12d9/0x1c90 security/integrity/ima/ima_main.c:407
       ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:667
       security_file_post_open+0xb3/0x260 security/security.c:2653
       do_open fs/namei.c:4679 [inline]
       path_openat+0x2e88/0x38a0 fs/namei.c:4836
       do_file_open+0x23e/0x4a0 fs/namei.c:4865
       do_sys_openat2+0x113/0x200 fs/open.c:1366
       do_sys_open fs/open.c:1372 [inline]
       __do_sys_openat fs/open.c:1388 [inline]
       __se_sys_openat fs/open.c:1383 [inline]
       __x64_sys_openat+0x138/0x170 fs/open.c:1383
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (btrfs_trans_num_writers){++++}-{0:0}:
       __lock_release kernel/locking/lockdep.c:5574 [inline]
       lock_release+0x199/0x3d0 kernel/locking/lockdep.c:5889
       percpu_up_read include/linux/percpu-rwsem.h:112 [inline]
       __sb_end_write include/linux/fs/super.h:14 [inline]
       sb_end_intwrite+0x26/0x1c0 include/linux/fs/super.h:101
       __btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1085
       btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6457
       touch_atime+0x2f8/0x6b0 fs/inode.c:2271
       file_accessed include/linux/fs.h:2263 [inline]
       btrfs_file_mmap_prepare+0x189/0x200 fs/btrfs/file.c:2051
       vfs_mmap_prepare include/linux/fs.h:2075 [inline]
       call_mmap_prepare mm/vma.c:2644 [inline]
       __mmap_region mm/vma.c:2743 [inline]
       mmap_region+0xdf2/0x2190 mm/vma.c:2844
       do_mmap+0xc2f/0x10c0 mm/mmap.c:559
       vm_mmap_pgoff+0x2cc/0x4f0 mm/util.c:581
       ksys_mmap_pgoff+0x4e8/0x720 mm/mmap.c:605
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/0xf80 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 kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
       down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1560
       mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601
       get_mmap_lock_carefully mm/mmap_lock.c:450 [inline]
       lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501
       do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357
       handle_page_fault arch/x86/mm/fault.c:1474 [inline]
       exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527
       asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
       user_access_begin arch/x86/include/asm/uaccess.h:-1 [inline]
       filldir+0x29b/0x690 fs/readdir.c:290
       dir_emit_dot include/linux/fs.h:3570 [inline]
       dir_emit_dots include/linux/fs.h:3581 [inline]
       offset_readdir+0x1aa/0x530 fs/libfs.c:562
       iterate_dir+0x3a5/0x580 fs/readdir.c:108
       __do_sys_getdents fs/readdir.c:327 [inline]
       __se_sys_getdents+0xf1/0x270 fs/readdir.c:312
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x14d/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:
  &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.5.751/18688:
 #0: ffff88803ad5c928 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x252/0x320 fs/file.c:1261
 #1: ffff88803b001c78 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x29e/0x580 fs/readdir.c:101

stack backtrace:
CPU: 0 UID: 0 PID: 18688 Comm: syz.5.751 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 down_read_killable+0xa4/0x220 kernel/locking/rwsem.c:1560
 mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:601
 get_mmap_lock_carefully mm/mmap_lock.c:450 [inline]
 lock_mm_and_find_vma+0x2d7/0x340 mm/mmap_lock.c:501
 do_user_addr_fault+0x330/0x1340 arch/x86/mm/fault.c:1357
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x6a/0xc0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0010:filldir+0x29b/0x690 fs/readdir.c:294
Code: 86 ff 4c 89 ff 4c 89 e6 e8 92 96 86 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:ffffc9000488fc70 EFLAGS: 00050287
RAX: 0000000000000000 RBX: ffffc9000488fe38 RCX: ffff8880381d9e80
RDX: 0000000000000000 RSI: 0000200000001fc0 RDI: 0000200000001fd8
RBP: 00007ffffffff000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000100 R11: ffffffff823def50 R12: 0000200000001fc0
R13: ffffffff8b5dc340 R14: 0000000000000001 R15: 0000200000001fd8
 dir_emit_dot include/linux/fs.h:3570 [inline]
 dir_emit_dots include/linux/fs.h:3581 [inline]
 offset_readdir+0x1aa/0x530 fs/libfs.c:562
 iterate_dir+0x3a5/0x580 fs/readdir.c:108
 __do_sys_getdents fs/readdir.c:327 [inline]
 __se_sys_getdents+0xf1/0x270 fs/readdir.c:312
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7feb9d4ac819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007feb9b6e5028 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007feb9d726090 RCX: 00007feb9d4ac819
RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000004
RBP: 00007feb9d542c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007feb9d726128 R14: 00007feb9d726090 R15: 00007fff42736dc8
 </TASK>
----------------
Code disassembly (best guess):
   0:	86 ff                	xchg   %bh,%bh
   2:	4c 89 ff             	mov    %r15,%rdi
   5:	4c 89 e6             	mov    %r12,%rsi
   8:	e8 92 96 86 ff       	call   0xff86969f
   d:	4d 39 e7             	cmp    %r12,%r15
  10:	0f 82 7c 02 00 00    	jb     0x292
  16:	49 39 ef             	cmp    %rbp,%r15
  19:	0f 87 73 02 00 00    	ja     0x292
  1f:	0f 01 cb             	stac
  22:	0f ae e8             	lfence
  25:	48 8b 44 24 50       	mov    0x50(%rsp),%rax
* 2a:	49 89 44 24 08       	mov    %rax,0x8(%r12) <-- trapping instruction
  2f:	48 8b 4c 24 08       	mov    0x8(%rsp),%rcx
  34:	48 8b 44 24 58       	mov    0x58(%rsp),%rax
  39:	48 89 01             	mov    %rax,(%rcx)
  3c:	48 8b 04 24          	mov    (%rsp),%rax