======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.2.4336/24893 is trying to acquire lock:
ffff888024a42800 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock_killable+0x1d/0x70 include/linux/mmap_lock.h:400
but task is already holding lock:
ffff888053bd5068 (&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:
-> #5 (&type->i_mutex_dir_key#5){++++}-{4:4}:
down_read+0x47/0x2e0 kernel/locking/rwsem.c:1537
inode_lock_shared include/linux/fs.h:1042 [inline]
lookup_slow+0x46/0x70 fs/namei.c:1874
walk_component fs/namei.c:2221 [inline]
lookup_last fs/namei.c:2722 [inline]
path_lookupat+0x3f5/0x8c0 fs/namei.c:2746
filename_lookup+0x212/0x570 fs/namei.c:2775
kern_path+0x35/0x50 fs/namei.c:2987
is_same_device fs/btrfs/volumes.c:759 [inline]
device_list_add+0xe21/0x22b0 fs/btrfs/volumes.c:893
btrfs_scan_one_device+0x3ef/0x680 fs/btrfs/volumes.c:1492
btrfs_get_tree_super fs/btrfs/super.c:1860 [inline]
btrfs_get_tree_subvol fs/btrfs/super.c:2089 [inline]
btrfs_get_tree+0x4ab/0x1920 fs/btrfs/super.c:2123
vfs_get_tree+0x92/0x2a0 fs/super.c:1751
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #4 (&fs_devs->device_list_mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:614 [inline]
__mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
btrfs_run_dev_stats+0xf6/0x1030 fs/btrfs/volumes.c:7722
commit_cowonly_roots+0x1b2/0x860 fs/btrfs/transaction.c:1357
btrfs_commit_transaction+0x105b/0x3b10 fs/btrfs/transaction.c:2477
btrfs_rebuild_free_space_tree+0x28b/0x6c0 fs/btrfs/free-space-tree.c:1375
btrfs_start_pre_rw_mount+0x128f/0x1bf0 fs/btrfs/disk-io.c:3052
open_ctree+0x2b11/0x3d20 fs/btrfs/disk-io.c:3603
btrfs_fill_super fs/btrfs/super.c:983 [inline]
btrfs_get_tree_super fs/btrfs/super.c:1946 [inline]
btrfs_get_tree_subvol fs/btrfs/super.c:2089 [inline]
btrfs_get_tree+0x1061/0x1920 fs/btrfs/super.c:2123
vfs_get_tree+0x92/0x2a0 fs/super.c:1751
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #3 (&fs_info->reloc_mutex){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:614 [inline]
__mutex_lock+0x187/0x1350 kernel/locking/mutex.c:776
btrfs_commit_transaction+0xf6b/0x3b10 fs/btrfs/transaction.c:2423
btrfs_rebuild_free_space_tree+0x28b/0x6c0 fs/btrfs/free-space-tree.c:1375
btrfs_start_pre_rw_mount+0x128f/0x1bf0 fs/btrfs/disk-io.c:3052
open_ctree+0x2b11/0x3d20 fs/btrfs/disk-io.c:3603
btrfs_fill_super fs/btrfs/super.c:983 [inline]
btrfs_get_tree_super fs/btrfs/super.c:1946 [inline]
btrfs_get_tree_subvol fs/btrfs/super.c:2089 [inline]
btrfs_get_tree+0x1061/0x1920 fs/btrfs/super.c:2123
vfs_get_tree+0x92/0x2a0 fs/super.c:1751
fc_mount fs/namespace.c:1199 [inline]
do_new_mount_fc fs/namespace.c:3636 [inline]
do_new_mount+0x302/0xa10 fs/namespace.c:3712
do_mount fs/namespace.c:4035 [inline]
__do_sys_mount fs/namespace.c:4224 [inline]
__se_sys_mount+0x313/0x410 fs/namespace.c:4201
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (btrfs_trans_unblocked){++++}-{0:0}:
wait_current_trans+0x22b/0x520 fs/btrfs/transaction.c:533
start_transaction+0x6d2/0x15f0 fs/btrfs/transaction.c:709
btrfs_ioctl_qgroup_limit+0x108/0x230 fs/btrfs/ioctl.c:3814
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (sb_internal#3){.+.+}-{0:0}:
percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline]
percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
__sb_start_write include/linux/fs/super.h:19 [inline]
sb_start_intwrite include/linux/fs/super.h:177 [inline]
start_transaction+0x56f/0x15f0 fs/btrfs/transaction.c:701
btrfs_dirty_inode+0x9f/0x190 fs/btrfs/inode.c:6324
inode_update_time fs/inode.c:2167 [inline]
touch_atime+0x2f9/0x6d0 fs/inode.c:2240
file_accessed include/linux/fs.h:2254 [inline]
btrfs_file_mmap_prepare+0x176/0x1f0 fs/btrfs/file.c:2053
vfs_mmap_prepare include/linux/fs.h:2058 [inline]
call_mmap_prepare mm/vma.c:2596 [inline]
__mmap_region mm/vma.c:2692 [inline]
mmap_region+0xb2b/0x1d10 mm/vma.c:2786
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/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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x117/0x340 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:400
get_mmap_lock_carefully mm/mmap_lock.c:399 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:450
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
filldir+0x2b6/0x6c0 fs/readdir.c:295
dir_emit include/linux/fs.h:3527 [inline]
offset_dir_emit fs/libfs.c:499 [inline]
offset_iterate_dir fs/libfs.c:515 [inline]
offset_readdir+0x44c/0x560 fs/libfs.c:564
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/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.2.4336/24893:
#0: ffff8880661b60f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x247/0x320 fs/file.c:1255
#1: ffff888053bd5068 (&type->i_mutex_dir_key#5){++++}-{4:4}, at: iterate_dir+0x292/0x570 fs/readdir.c:101
stack backtrace:
CPU: 0 UID: 0 PID: 24893 Comm: syz.2.4336 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
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+0x2e2/0x300 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+0x15a6/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x117/0x340 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:400
get_mmap_lock_carefully mm/mmap_lock.c:399 [inline]
lock_mm_and_find_vma+0x2a8/0x300 mm/mmap_lock.c:450
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+0x2b6/0x6c0 fs/readdir.c:296
Code: 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 8b 54 24 1c <66> 89 41 10 80 e2 0f 41 89 c7 42 88 54 39 ff 49 63 ee c6 44 29 12
RSP: 0018:ffffc9000470fc90 EFLAGS: 00050283
RAX: 0000000000000020 RBX: ffffc9000470fe38 RCX: 0000200000001ff0
RDX: 000000000000000a RSI: 0000200000001fd8 RDI: 0000200000002010
RBP: 00007ffffffff000 R08: ffff88803ee9bd07 R09: 1ffff11007dd37a0
R10: dffffc0000000000 R11: ffffed1007dd37a1 R12: 0000200000001fd8
R13: ffff888076c501e8 R14: 0000000000000008 R15: 0000200000002010
dir_emit include/linux/fs.h:3527 [inline]
offset_dir_emit fs/libfs.c:499 [inline]
offset_iterate_dir fs/libfs.c:515 [inline]
offset_readdir+0x44c/0x560 fs/libfs.c:564
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/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9988d8f749
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:00007f9989c8b038 EFLAGS: 00000246 ORIG_RAX: 000000000000004e
RAX: ffffffffffffffda RBX: 00007f9988fe6180 RCX: 00007f9988d8f749
RDX: 00000000000000b8 RSI: 0000200000001fc0 RDI: 0000000000000005
RBP: 00007f9988e13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9988fe6218 R14: 00007f9988fe6180 R15: 00007fff640ee4d8
</TASK>
----------------
Code disassembly (best guess):
0: 87 73 02 xchg %esi,0x2(%rbx)
3: 00 00 add %al,(%rax)
5: 0f 01 cb stac
8: 0f ae e8 lfence
b: 48 8b 44 24 50 mov 0x50(%rsp),%rax
10: 49 89 44 24 08 mov %rax,0x8(%r12)
15: 48 8b 4c 24 08 mov 0x8(%rsp),%rcx
1a: 48 8b 44 24 58 mov 0x58(%rsp),%rax
1f: 48 89 01 mov %rax,(%rcx)
22: 48 8b 04 24 mov (%rsp),%rax
26: 8b 54 24 1c mov 0x1c(%rsp),%edx
* 2a: 66 89 41 10 mov %ax,0x10(%rcx) <-- trapping instruction
2e: 80 e2 0f and $0xf,%dl
31: 41 89 c7 mov %eax,%r15d
34: 42 88 54 39 ff mov %dl,-0x1(%rcx,%r15,1)
39: 49 63 ee movslq %r14d,%rbp
3c: c6 .byte 0xc6
3d: 44 29 12 sub %r10d,(%rdx)