syzbot

loop0: detected capacity change from 0 to 1024
============================================
WARNING: possible recursive locking detected
syzkaller #0 Not tainted
--------------------------------------------
syz.0.17/6068 is trying to acquire lock:
ffff88803be8a0a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfsplus_find_init+0x168/0x2d0 fs/hfsplus/bfind.c:28

but task is already holding lock:
ffff88803be8a0a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfsplus_find_init+0x168/0x2d0 fs/hfsplus/bfind.c:28

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.0.17/6068:
 #0: ffff888036890480 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:499
 #1: ffff888035d5b058 (&sb->s_type->i_mutex_key#23){+.+.}-{4:4}, at: inode_lock_killable include/linux/fs.h:1032 [inline]
 #1: ffff888035d5b058 (&sb->s_type->i_mutex_key#23){+.+.}-{4:4}, at: do_truncate+0x171/0x220 fs/open.c:63
 #2: ffff888035d5adf8 (&hip->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x1f8/0x1c40 fs/hfsplus/extents.c:453
 #3: ffff88803be8a0a0 (&tree->tree_lock/1){+.+.}-{4:4}, at: hfsplus_find_init+0x168/0x2d0 fs/hfsplus/bfind.c:28
 #4: ffff888035d580f8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{4:4}, at: hfsplus_file_extend+0x1f8/0x1c40 fs/hfsplus/extents.c:453

stack backtrace:
CPU: 1 UID: 0 PID: 6068 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(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_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041
 check_deadlock kernel/locking/lockdep.c:3093 [inline]
 validate_chain kernel/locking/lockdep.c:3895 [inline]
 __lock_acquire+0x2540/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x117/0x340 kernel/locking/lockdep.c:5868
 __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline]
 mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552
 hfsplus_find_init+0x168/0x2d0 fs/hfsplus/bfind.c:28
 hfsplus_ext_read_extent fs/hfsplus/extents.c:216 [inline]
 hfsplus_file_extend+0x40e/0x1c40 fs/hfsplus/extents.c:457
 hfsplus_bmap_reserve+0x128/0x520 fs/hfsplus/btree.c:358
 __hfsplus_ext_write_extent+0x2b0/0x5e0 fs/hfsplus/extents.c:104
 __hfsplus_ext_cache_extent+0x9f/0xd40 fs/hfsplus/extents.c:186
 hfsplus_ext_read_extent fs/hfsplus/extents.c:218 [inline]
 hfsplus_file_extend+0x437/0x1c40 fs/hfsplus/extents.c:457
 hfsplus_get_block+0x40c/0x1600 fs/hfsplus/extents.c:245
 __block_write_begin_int+0x6b5/0x1900 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x78c/0xb50 fs/buffer.c:2594
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 cont_expand_zero fs/buffer.c:2522 [inline]
 cont_write_begin+0x2fd/0xb50 fs/buffer.c:2584
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 generic_cont_expand_simple+0x13f/0x210 fs/buffer.c:2485
 hfsplus_setattr+0x169/0x270 fs/hfsplus/inode.c:280
 notify_change+0xc18/0xf60 fs/attr.c:546
 do_truncate+0x1a4/0x220 fs/open.c:68
 vfs_truncate+0x493/0x520 fs/open.c:118
 do_sys_truncate+0xdb/0x190 fs/open.c:141
 __do_sys_truncate fs/open.c:153 [inline]
 __se_sys_truncate fs/open.c:151 [inline]
 __x64_sys_truncate+0x5b/0x70 fs/open.c:151
 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: 0033:0x7f577db9f749
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:00007ffc9a398998 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f577ddf5fa0 RCX: 00007f577db9f749
RDX: 0000000000000000 RSI: 0000000003000000 RDI: 0000200000000900
RBP: 00007f577dc23f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f577ddf5fa0 R14: 00007f577ddf5fa0 R15: 0000000000000002
 </TASK>
------------[ cut here ]------------
rtmutex deadlock detected
WARNING: kernel/locking/rtmutex.c:1674 at 0x0, CPU#1: syz.0.17/6068
Modules linked in:
CPU: 1 UID: 0 PID: 6068 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:rt_mutex_handle_deadlock+0x21/0xb0 kernel/locking/rtmutex.c:1674
Code: 90 90 90 90 90 90 90 90 90 41 57 41 56 41 55 41 54 53 83 ff dd 0f 85 86 00 00 00 48 89 f7 e8 66 3b 01 00 48 8d 3d cf a8 08 04 <67> 48 0f b9 3a 4c 8d 3d 00 00 00 00 65 48 8b 1c 25 08 e0 b0 91 4c
RSP: 0018:ffffc90004826d30 EFLAGS: 00010286
RAX: 0000000080000000 RBX: ffffc90004826dc0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8b3efa40 RDI: ffffffff8eddb8f0
RBP: ffffc90004826ec8 R08: ffffffff8eda9677 R09: 1ffffffff1db52ce
R10: dffffc0000000000 R11: fffffbfff1db52cf R12: 1ffff92000904db4
R13: ffffffff8ad50b09 R14: ffff88803be8a048 R15: dffffc0000000000
FS:  000055556e5da500(0000) GS:ffff888126e12000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe6aff5eec CR3: 000000003c24c000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1734 [inline]
 __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1760 [inline]
 rt_mutex_slowlock+0x666/0x6b0 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:534 [inline]
 mutex_lock_nested+0x16a/0x1d0 kernel/locking/rtmutex_api.c:552
 hfsplus_find_init+0x168/0x2d0 fs/hfsplus/bfind.c:28
 hfsplus_ext_read_extent fs/hfsplus/extents.c:216 [inline]
 hfsplus_file_extend+0x40e/0x1c40 fs/hfsplus/extents.c:457
 hfsplus_bmap_reserve+0x128/0x520 fs/hfsplus/btree.c:358
 __hfsplus_ext_write_extent+0x2b0/0x5e0 fs/hfsplus/extents.c:104
 __hfsplus_ext_cache_extent+0x9f/0xd40 fs/hfsplus/extents.c:186
 hfsplus_ext_read_extent fs/hfsplus/extents.c:218 [inline]
 hfsplus_file_extend+0x437/0x1c40 fs/hfsplus/extents.c:457
 hfsplus_get_block+0x40c/0x1600 fs/hfsplus/extents.c:245
 __block_write_begin_int+0x6b5/0x1900 fs/buffer.c:2145
 block_write_begin fs/buffer.c:2256 [inline]
 cont_write_begin+0x78c/0xb50 fs/buffer.c:2594
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 cont_expand_zero fs/buffer.c:2522 [inline]
 cont_write_begin+0x2fd/0xb50 fs/buffer.c:2584
 hfsplus_write_begin+0x66/0xb0 fs/hfsplus/inode.c:48
 generic_cont_expand_simple+0x13f/0x210 fs/buffer.c:2485
 hfsplus_setattr+0x169/0x270 fs/hfsplus/inode.c:280
 notify_change+0xc18/0xf60 fs/attr.c:546
 do_truncate+0x1a4/0x220 fs/open.c:68
 vfs_truncate+0x493/0x520 fs/open.c:118
 do_sys_truncate+0xdb/0x190 fs/open.c:141
 __do_sys_truncate fs/open.c:153 [inline]
 __se_sys_truncate fs/open.c:151 [inline]
 __x64_sys_truncate+0x5b/0x70 fs/open.c:151
 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: 0033:0x7f577db9f749
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:00007ffc9a398998 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007f577ddf5fa0 RCX: 00007f577db9f749
RDX: 0000000000000000 RSI: 0000000003000000 RDI: 0000200000000900
RBP: 00007f577dc23f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f577ddf5fa0 R14: 00007f577ddf5fa0 R15: 0000000000000002
 </TASK>
----------------
Code disassembly (best guess):
   0:	90                   	nop
   1:	90                   	nop
   2:	90                   	nop
   3:	90                   	nop
   4:	90                   	nop
   5:	90                   	nop
   6:	90                   	nop
   7:	90                   	nop
   8:	90                   	nop
   9:	41 57                	push   %r15
   b:	41 56                	push   %r14
   d:	41 55                	push   %r13
   f:	41 54                	push   %r12
  11:	53                   	push   %rbx
  12:	83 ff dd             	cmp    $0xffffffdd,%edi
  15:	0f 85 86 00 00 00    	jne    0xa1
  1b:	48 89 f7             	mov    %rsi,%rdi
  1e:	e8 66 3b 01 00       	call   0x13b89
  23:	48 8d 3d cf a8 08 04 	lea    0x408a8cf(%rip),%rdi        # 0x408a8f9
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	4c 8d 3d 00 00 00 00 	lea    0x0(%rip),%r15        # 0x36
  36:	65 48 8b 1c 25 08 e0 	mov    %gs:0xffffffff91b0e008,%rbx
  3d:	b0 91
  3f:	4c                   	rex.WR