[v5.15] possible deadlock in reiserfs_lookup

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cc5ec8769306 Linux 5.15.196
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15cb0f42580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=3b42a532aa7c3ec26090
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c71c660545b2/disk-cc5ec876.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4f011826cca6/vmlinux-cc5ec876.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8ccd1a2c3f8c/bzImage-cc5ec876.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3b42a5...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.1182/9148 is trying to acquire lock:
ffff88807502ea28 (&mm->mmap_lock){++++}-{3:3}, at: __might_fault+0x90/0x110 mm/memory.c:5356

but task is already holding lock:
ffff888060d5b090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock+0x75/0xd0 fs/reiserfs/lock.c:27

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #5 (&sbi->lock){+.+.}-{3:3}:
__mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
reiserfs_write_lock+0x75/0xd0 fs/reiserfs/lock.c:27
reiserfs_lookup+0x137/0x420 fs/reiserfs/namei.c:364
__lookup_slow+0x27d/0x3d0 fs/namei.c:1671
lookup_one_len+0x18e/0x2c0 fs/namei.c:2726
reiserfs_lookup_privroot+0x85/0x1e0 fs/reiserfs/xattr.c:980
reiserfs_fill_super+0x1f65/0x23e0 fs/reiserfs/super.c:2178
mount_bdev+0x287/0x3c0 fs/super.c:1400
legacy_get_tree+0xe6/0x180 fs/fs_context.c:611
vfs_get_tree+0x88/0x270 fs/super.c:1530
do_new_mount+0x24a/0xa40 fs/namespace.c:3034
do_mount fs/namespace.c:3377 [inline]
__do_sys_mount fs/namespace.c:3585 [inline]
__se_sys_mount+0x2d6/0x3c0 fs/namespace.c:3562
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #4 (&type->i_mutex_dir_key#15){++++}-{3:3}:
down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
inode_lock_shared include/linux/fs.h:797 [inline]
lookup_slow+0x46/0x70 fs/namei.c:1687
walk_component+0x319/0x460 fs/namei.c:1984
lookup_last fs/namei.c:2439 [inline]
path_lookupat+0x169/0x440 fs/namei.c:2463
filename_lookup+0x1e2/0x4f0 fs/namei.c:2492
kern_path+0x37/0x190 fs/namei.c:2590
lookup_bdev+0xbd/0x270 block/bdev.c:982
device_matched fs/btrfs/volumes.c:568 [inline]
btrfs_free_stale_devices+0x6db/0xa60 fs/btrfs/volumes.c:608
btrfs_forget_devices+0x52/0x80 fs/btrfs/volumes.c:1431
btrfs_control_ioctl+0x104/0x220 fs/btrfs/super.c:2450
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #3 (&fs_devs->device_list_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
btrfs_run_dev_stats+0xdf/0xdf0 fs/btrfs/volumes.c:7991
commit_cowonly_roots+0x17e/0x9c0 fs/btrfs/transaction.c:1292
btrfs_commit_transaction+0x1229/0x3440 fs/btrfs/transaction.c:2394
close_ctree+0x3d5/0x8c0 fs/btrfs/disk-io.c:4470
generic_shutdown_super+0x130/0x300 fs/super.c:475
kill_anon_super+0x36/0x70 fs/super.c:1089
btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2390
deactivate_locked_super+0x93/0xf0 fs/super.c:335
cleanup_mnt+0x418/0x4d0 fs/namespace.c:1148
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (&fs_info->tree_log_mutex){+.+.}-{3:3}:
__lock_release kernel/locking/lockdep.c:5339 [inline]
lock_release+0x31a/0x870 kernel/locking/lockdep.c:5643
__mutex_unlock_slowpath+0xb3/0x6a0 kernel/locking/mutex.c:851
btrfs_commit_transaction+0x1c11/0x3440 fs/btrfs/transaction.c:2441
close_ctree+0x3d5/0x8c0 fs/btrfs/disk-io.c:4470
generic_shutdown_super+0x130/0x300 fs/super.c:475
kill_anon_super+0x36/0x70 fs/super.c:1089
btrfs_kill_super+0x3d/0x50 fs/btrfs/super.c:2390
deactivate_locked_super+0x93/0xf0 fs/super.c:335
cleanup_mnt+0x418/0x4d0 fs/namespace.c:1148
task_work_run+0x125/0x1a0 kernel/task_work.c:188
tracehook_notify_resume include/linux/tracehook.h:189 [inline]
exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
__syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (sb_internal#2){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1811 [inline]
sb_start_intwrite include/linux/fs.h:1928 [inline]
start_transaction+0x5bc/0x1130 fs/btrfs/transaction.c:680
btrfs_dirty_inode+0xc5/0x1c0 fs/btrfs/inode.c:6451
inode_update_time fs/inode.c:1893 [inline]
touch_atime+0x2f6/0x620 fs/inode.c:1966
file_accessed include/linux/fs.h:2522 [inline]
btrfs_file_mmap+0xc1/0x120 fs/btrfs/file.c:2449
call_mmap include/linux/fs.h:2178 [inline]
mmap_file+0x5d/0xb0 mm/util.c:1092
__mmap_region mm/mmap.c:1796 [inline]
mmap_region+0xf8f/0x1660 mm/mmap.c:2933
do_mmap+0x81f/0xea0 mm/mmap.c:1586
vm_mmap_pgoff+0x1b2/0x2b0 mm/util.c:551
ksys_mmap_pgoff+0x542/0x780 mm/mmap.c:1635
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (&mm->mmap_lock){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
__might_fault+0xb3/0x110 mm/memory.c:5357
reiserfs_ioctl+0x13b/0x330 fs/reiserfs/ioctl.c:96
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
&mm->mmap_lock --> &type->i_mutex_dir_key#15 --> &sbi->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sbi->lock);
lock(&type->i_mutex_dir_key#15);
lock(&sbi->lock);
lock(&mm->mmap_lock);

*** DEADLOCK ***

1 lock held by syz.4.1182/9148:
#0: ffff888060d5b090 (&sbi->lock){+.+.}-{3:3}, at: reiserfs_write_lock+0x75/0xd0 fs/reiserfs/lock.c:27

stack backtrace:
CPU: 1 PID: 9148 Comm: syz.4.1182 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
check_prev_add kernel/locking/lockdep.c:3053 [inline]
check_prevs_add kernel/locking/lockdep.c:3172 [inline]
validate_chain kernel/locking/lockdep.c:3788 [inline]
__lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
__might_fault+0xb3/0x110 mm/memory.c:5357
reiserfs_ioctl+0x13b/0x330 fs/reiserfs/ioctl.c:96
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f3c2a7b0749
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:00007f3c28a17038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f3c2aa06fa0 RCX: 00007f3c2a7b0749
RDX: 0000200000000000 RSI: 0000000080087601 RDI: 0000000000000004
RBP: 00007f3c2a834f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3c2aa07038 R14: 00007f3c2aa06fa0 R15: 00007fff6ae0a188
</TASK>


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