======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.8342/8264 is trying to acquire lock:
ffff88807799d7e0 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377
but task is already holding lock:
ffff8880289349f0 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x292/0x570 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+0x46/0x2e0 kernel/locking/rwsem.c:1537
inode_lock_shared include/linux/fs.h:995 [inline]
lookup_slow+0x46/0x70 fs/namei.c:1832
walk_component+0x2d2/0x400 fs/namei.c:2151
lookup_last fs/namei.c:2652 [inline]
path_lookupat+0x163/0x430 fs/namei.c:2676
filename_lookup+0x212/0x570 fs/namei.c:2705
kern_path+0x35/0x50 fs/namei.c:2863
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:1865 [inline]
btrfs_get_tree_subvol fs/btrfs/super.c:2094 [inline]
btrfs_get_tree+0x4ab/0x1920 fs/btrfs/super.c:2128
vfs_get_tree+0x92/0x2b0 fs/super.c:1758
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3642 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3718
do_mount fs/namespace.c:4041 [inline]
__do_sys_mount fs/namespace.c:4229 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4206
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 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/mutex.c:598 [inline]
__mutex_lock+0x187/0x1350 kernel/locking/mutex.c:760
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_metadata_space+0x144/0x390 fs/btrfs/space-info.c:1158
btrfs_async_reclaim_metadata_space+0x89/0xe0 fs/btrfs/space-info.c:1226
process_one_work kernel/workqueue.c:3263 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 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}:
lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
join_transaction+0x1a4/0xd70 fs/btrfs/transaction.c:321
start_transaction+0x6b6/0x1620 fs/btrfs/transaction.c:705
btrfs_setxattr_trans+0xcc/0x380 fs/btrfs/xattr.c:240
__vfs_setxattr+0x43c/0x480 fs/xattr.c:200
__vfs_setxattr_noperm+0x12d/0x660 fs/xattr.c:234
vfs_setxattr+0x16b/0x2f0 fs/xattr.c:321
do_setxattr fs/xattr.c:636 [inline]
filename_setxattr+0x274/0x600 fs/xattr.c:665
path_setxattrat+0x364/0x3a0 fs/xattr.c:713
__do_sys_setxattr fs/xattr.c:747 [inline]
__se_sys_setxattr fs/xattr.c:743 [inline]
__x64_sys_setxattr+0xbc/0xe0 fs/xattr.c:743
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 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:1911 [inline]
sb_end_intwrite+0x26/0x1c0 include/linux/fs.h:2028
__btrfs_end_transaction+0x248/0x640 fs/btrfs/transaction.c:1076
btrfs_dirty_inode+0x14c/0x190 fs/btrfs/inode.c:6286
inode_update_time fs/inode.c:2129 [inline]
touch_atime+0x2f9/0x6d0 fs/inode.c:2202
file_accessed include/linux/fs.h:2673 [inline]
btrfs_file_mmap_prepare+0xd5/0x140 fs/btrfs/file.c:2049
vfs_mmap_prepare include/linux/fs.h:2410 [inline]
call_mmap_prepare mm/vma.c:2586 [inline]
__mmap_region mm/vma.c:2654 [inline]
mmap_region+0xb47/0x2110 mm/vma.c:2740
do_mmap+0xc45/0x10d0 mm/mmap.c:558
vm_mmap_pgoff+0x2a6/0x4d0 mm/util.c:581
ksys_mmap_pgoff+0x51f/0x760 mm/mmap.c:604
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xfa0 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+0x50/0x350 kernel/locking/rwsem.c:1560
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377
get_mmap_lock_carefully mm/mmap_lock.c:377 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:428
do_user_addr_fault+0x331/0x1380 arch/x86/mm/fault.c:1359
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
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+0x29c/0x6c0 fs/readdir.c:290
dir_emit_dot include/linux/fs.h:3992 [inline]
dir_emit_dots include/linux/fs.h:4003 [inline]
offset_readdir+0x1e6/0x560 fs/libfs.c:569
iterate_dir+0x399/0x570 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/0xfa0 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.1.8342/8264:
#0: ffff88802f7d60f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1232
#1: ffff8880289349f0 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x292/0x570 fs/readdir.c:101
stack backtrace:
CPU: 0 UID: 0 PID: 8264 Comm: syz.1.8342 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
<TASK>
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+0x50/0x350 kernel/locking/rwsem.c:1560
mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:377
get_mmap_lock_carefully mm/mmap_lock.c:377 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:428
do_user_addr_fault+0x331/0x1380 arch/x86/mm/fault.c:1359
handle_page_fault arch/x86/mm/fault.c:1476 [inline]
exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0010:filldir+0x29c/0x6c0 fs/readdir.c:294
Code: 83 ff 4c 89 ff 4c 89 e6 e8 31 dc 83 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:ffffc9000469fc90 EFLAGS: 00050287
RAX: 0000000000000000 RBX: ffffc9000469fe38 RCX: ffff888025869e40
RDX: 0000000000000000 RSI: 0000200000001fc0 RDI: 0000200000001fd8
RBP: 00007ffffffff000 R08: 000000000000054a R09: 0000000000000004
R10: 000000007fffffff R11: ffffffff823c2770 R12: 0000200000001fc0
R13: ffffffff8b79be60 R14: 0000000000000001 R15: 0000200000001fd8
dir_emit_dot include/linux/fs.h:3992 [inline]
dir_emit_dots include/linux/fs.h:4003 [inline]
offset_readdir+0x1e6/0x560 fs/libfs.c:569
iterate_dir+0x399/0x570 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/0xfa0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdb0e18f749
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:00007fdb0efe6038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007fdb0e3e6180 RCX: 00007fdb0e18f749
RDX: 0000000020002078 RSI: 0000200000001fc0 RDI: 0000000000000008
RBP: 00007fdb0e213f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb0e3e6218 R14: 00007fdb0e3e6180 R15: 00007ffdcdf695a8
</TASK>
----------------
Code disassembly (best guess):
0: 83 ff 4c cmp $0x4c,%edi
3: 89 ff mov %edi,%edi
5: 4c 89 e6 mov %r12,%rsi
8: e8 31 dc 83 ff call 0xff83dc3e
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