[v6.6] possible deadlock in hfs_find_init

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c2603c511feb Linux 6.6.93
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14bf790c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=486bade17c8c30b9
dashboard link: https://syzkaller.appspot.com/bug?extid=949537796ff26787d134
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8754f950a6e7/disk-c2603c51.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3b19332dbf63/vmlinux-c2603c51.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cb245e836038/bzImage-c2603c51.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+949537...@syzkaller.appspotmail.com

loop7: detected capacity change from 0 to 64
======================================================
WARNING: possible circular locking dependency detected
6.6.93-syzkaller #0 Not tainted
------------------------------------------------------
syz.7.3583/19761 is trying to acquire lock:
ffff88807b0280b0 (&tree->tree_lock#2/1){+.+.}-{3:3}, at: hfs_find_init+0x15f/0x1d0 fs/hfs/bfind.c:-1

but task is already holding lock:
ffff88805fab8df8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397
hfs_bmap_reserve+0x107/0x430 fs/hfs/btree.c:234
__hfs_ext_write_extent+0x1fa/0x470 fs/hfs/extent.c:121
__hfs_ext_cache_extent+0x6b/0x9b0 fs/hfs/extent.c:174
hfs_ext_read_extent fs/hfs/extent.c:202 [inline]
hfs_extend_file+0x317/0x1220 fs/hfs/extent.c:401
hfs_get_block+0x3d8/0xbd0 fs/hfs/extent.c:353
__block_write_begin_int+0x566/0x1ad0 fs/buffer.c:2124
__block_write_begin fs/buffer.c:2173 [inline]
block_write_begin+0x9a/0x1e0 fs/buffer.c:2234
cont_write_begin+0x5c8/0x7e0 fs/buffer.c:2591
hfs_write_begin+0x8b/0xd0 fs/hfs/inode.c:58
cont_expand_zero fs/buffer.c:2518 [inline]
cont_write_begin+0x2ad/0x7e0 fs/buffer.c:2581
hfs_write_begin+0x8b/0xd0 fs/hfs/inode.c:58
generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4016
generic_file_write_iter+0xaf/0x2e0 mm/filemap.c:4137
call_write_iter include/linux/fs.h:2018 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x43b/0x940 fs/read_write.c:584
ksys_pwrite64 fs/read_write.c:699 [inline]
__do_sys_pwrite64 fs/read_write.c:709 [inline]
__se_sys_pwrite64 fs/read_write.c:706 [inline]
__x64_sys_pwrite64+0x195/0x220 fs/read_write.c:706
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&tree->tree_lock#2/1){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
hfs_find_init+0x15f/0x1d0 fs/hfs/bfind.c:-1
hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
hfs_extend_file+0x2ef/0x1220 fs/hfs/extent.c:401
hfs_bmap_reserve+0x107/0x430 fs/hfs/btree.c:234
hfs_cat_create+0x1b4/0x620 fs/hfs/catalog.c:104
hfs_create+0x66/0xd0 fs/hfs/dir.c:202
lookup_open fs/namei.c:3488 [inline]
open_last_lookups fs/namei.c:3556 [inline]
path_openat+0x1277/0x3190 fs/namei.c:3786
do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_openat fs/open.c:1450 [inline]
__se_sys_openat fs/open.c:1445 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1445
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&HFS_I(tree->inode)->extents_lock);
lock(&tree->tree_lock#2/1);
lock(&HFS_I(tree->inode)->extents_lock);
lock(&tree->tree_lock#2/1);

*** DEADLOCK ***

4 locks held by syz.7.3583/19761:
#0: ffff88802469c418 (sb_writers#29){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:403
#1: ffff88805fabc3b8 (&type->i_mutex_dir_key#16){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
#1: ffff88805fabc3b8 (&type->i_mutex_dir_key#16){+.+.}-{3:3}, at: open_last_lookups fs/namei.c:3553 [inline]
#1: ffff88805fabc3b8 (&type->i_mutex_dir_key#16){+.+.}-{3:3}, at: path_openat+0x7c6/0x3190 fs/namei.c:3786
#2: ffff88807b02e0b0 (&tree->tree_lock#2){+.+.}-{3:3}, at: hfs_find_init+0x15f/0x1d0 fs/hfs/bfind.c:-1
#3: ffff88805fab8df8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397

stack backtrace:
CPU: 0 PID: 19761 Comm: syz.7.3583 Not tainted 6.6.93-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
check_noncircular+0x2bd/0x3c0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3869 [inline]
__lock_acquire+0x2ddb/0x7c80 kernel/locking/lockdep.c:5137
lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
hfs_find_init+0x15f/0x1d0 fs/hfs/bfind.c:-1
hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
hfs_extend_file+0x2ef/0x1220 fs/hfs/extent.c:401
hfs_bmap_reserve+0x107/0x430 fs/hfs/btree.c:234
hfs_cat_create+0x1b4/0x620 fs/hfs/catalog.c:104
hfs_create+0x66/0xd0 fs/hfs/dir.c:202
lookup_open fs/namei.c:3488 [inline]
open_last_lookups fs/namei.c:3556 [inline]
path_openat+0x1277/0x3190 fs/namei.c:3786
do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_openat fs/open.c:1450 [inline]
__se_sys_openat fs/open.c:1445 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1445
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f61be78e929
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:00007f61bf5b6038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f61be9b5fa0 RCX: 00007f61be78e929
RDX: 000000000000275a RSI: 0000200000000840 RDI: ffffffffffffff9c
RBP: 00007f61be810b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f61be9b5fa0 R15: 00007ffda8979ae8
</TASK>


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 4791134e4aeb Linux 6.6.118
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=136f501a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=949537796ff26787d134
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16566ab4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=116bd4c2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ca168ecfe887/disk-4791134e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/adda86b1a76b/vmlinux-4791134e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cc2019969cb7/bzImage-4791134e.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/e3a8addbc809/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+949537...@syzkaller.appspotmail.com

option from the mount to silence this warning.
=======================================================
hfs: unable to locate alternate MDB
hfs: continuing without an alternate MDB
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.17/5949 is trying to acquire lock:
ffff88802bc1a0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1

but task is already holding lock:

ffff88802bc1a0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0

----
lock(&tree->tree_lock/1);
lock(&tree->tree_lock/1);

*** DEADLOCK ***

May be due to missing lock nesting notation

5 locks held by syz.0.17/5949:
#0: ffff88802bc18418 (sb_writers#13){.+.+}-{0:0}, at: do_sys_ftruncate+0x281/0x3d0 fs/open.c:191
#1: ffff88802c4c8938 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
#1: ffff88802c4c8938 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: do_truncate+0x187/0x220 fs/open.c:64
#2: ffff88802c4c8778 (&HFS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397
#3: ffff88802bc1a0b0 (&tree->tree_lock/1){+.+.}-{3:3}, at: hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1
#4: ffff8880280000f8 (&HFS_I(tree->inode)->extents_lock){+.+.}-{3:3}, at: hfs_extend_file+0xdb/0x1220 fs/hfs/extent.c:397

stack backtrace:
CPU: 0 PID: 5949 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025

Call Trace:
<TASK>
dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106

check_deadlock kernel/locking/lockdep.c:3062 [inline]
validate_chain kernel/locking/lockdep.c:3856 [inline]
__lock_acquire+0x5d40/0x7c80 kernel/locking/lockdep.c:5137

lock_acquire+0x197/0x410 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747

hfs_find_init+0x17e/0x1f0 fs/hfs/bfind.c:-1

hfs_ext_read_extent fs/hfs/extent.c:200 [inline]
hfs_extend_file+0x2ef/0x1220 fs/hfs/extent.c:401

hfs_bmap_reserve+0x107/0x430 fs/hfs/btree.c:269

__hfs_ext_write_extent+0x1fa/0x470 fs/hfs/extent.c:121
__hfs_ext_cache_extent+0x6b/0x9b0 fs/hfs/extent.c:174
hfs_ext_read_extent fs/hfs/extent.c:202 [inline]
hfs_extend_file+0x317/0x1220 fs/hfs/extent.c:401
hfs_get_block+0x3d8/0xbd0 fs/hfs/extent.c:353
__block_write_begin_int+0x566/0x1ad0 fs/buffer.c:2124
__block_write_begin fs/buffer.c:2173 [inline]
block_write_begin+0x9a/0x1e0 fs/buffer.c:2234
cont_write_begin+0x5c8/0x7e0 fs/buffer.c:2591
hfs_write_begin+0x8b/0xd0 fs/hfs/inode.c:58
cont_expand_zero fs/buffer.c:2518 [inline]
cont_write_begin+0x2ad/0x7e0 fs/buffer.c:2581
hfs_write_begin+0x8b/0xd0 fs/hfs/inode.c:58

hfs_file_truncate+0x191/0x9b0 fs/hfs/extent.c:494
hfs_inode_setattr+0x4af/0x6e0 fs/hfs/inode.c:659
notify_change+0xb0d/0xe10 fs/attr.c:499
do_truncate+0x19b/0x220 fs/open.c:66
do_sys_ftruncate+0x325/0x3d0 fs/open.c:194

do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

RIP: 0033:0x7fd82d58f749

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:00007ffcf9284228 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 00007fd82d7e5fa0 RCX: 00007fd82d58f749
RDX: 0000000000000000 RSI: 0000000008800000 RDI: 0000000000000004
RBP: 00007fd82d613f91 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000

R13: 00007fd82d7e5fa0 R14: 00007fd82d7e5fa0 R15: 0000000000000002
</TASK>


---
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