syzbot

loop4: detected capacity change from 0 to 1024
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.4.178/6863 is trying to acquire lock:
ffff88807f3050f8 (&sbi->alloc_mutex){+.+.}-{3:3}, at: hfsplus_block_free+0xc3/0x4b0 fs/hfsplus/bitmap.c:182

but task is already holding lock:
ffff888077c087c8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_truncate+0x293/0xb40 fs/hfsplus/extents.c:574

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x129/0xcc0 kernel/locking/mutex.c:747
       hfsplus_get_block+0x39f/0x1530 fs/hfsplus/extents.c:260
       block_read_full_folio+0x42e/0xf40 fs/buffer.c:2406
       filemap_read_folio+0x167/0x760 mm/filemap.c:2420
       do_read_cache_folio+0x470/0x7e0 mm/filemap.c:3804
       do_read_cache_page+0x32/0x250 mm/filemap.c:3870
       read_mapping_page include/linux/pagemap.h:892 [inline]
       hfsplus_block_allocate+0xff/0x8e0 fs/hfsplus/bitmap.c:37
       hfsplus_file_extend+0xae4/0x1990 fs/hfsplus/extents.c:466
       hfsplus_get_block+0x412/0x1530 fs/hfsplus/extents.c:245
       __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
       hfsplus_write_begin+0x8b/0xd0 fs/hfsplus/inode.c:52
       generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4031
       generic_file_write_iter+0xaf/0x2e0 mm/filemap.c:4152
       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_write+0x147/0x250 fs/read_write.c:637
       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 (&sbi->alloc_mutex){+.+.}-{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
       hfsplus_block_free+0xc3/0x4b0 fs/hfsplus/bitmap.c:182
       hfsplus_free_extents+0x10d/0xa50 fs/hfsplus/extents.c:360
       hfsplus_file_truncate+0x735/0xb40 fs/hfsplus/extents.c:589
       hfsplus_setattr+0x1c3/0x280 fs/hfsplus/inode.c:269
       notify_change+0xb0d/0xe10 fs/attr.c:499
       do_truncate+0x19b/0x220 fs/open.c:66
       vfs_truncate+0x266/0x300 fs/open.c:112
       do_sys_truncate+0xe0/0x1a0 fs/open.c:135
       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(&HFSPLUS_I(inode)->extents_lock);
                               lock(&sbi->alloc_mutex);
                               lock(&HFSPLUS_I(inode)->extents_lock);
  lock(&sbi->alloc_mutex);

 *** DEADLOCK ***

3 locks held by syz.4.178/6863:
 #0: ffff88807afd0418 (sb_writers#15){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:412
 #1: ffff888077c089d0 (&sb->s_type->i_mutex_key#23){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
 #1: ffff888077c089d0 (&sb->s_type->i_mutex_key#23){+.+.}-{3:3}, at: do_truncate+0x187/0x220 fs/open.c:64
 #2: ffff888077c087c8 (&HFSPLUS_I(inode)->extents_lock){+.+.}-{3:3}, at: hfsplus_file_truncate+0x293/0xb40 fs/hfsplus/extents.c:574

stack backtrace:
CPU: 1 PID: 6863 Comm: syz.4.178 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_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
 hfsplus_block_free+0xc3/0x4b0 fs/hfsplus/bitmap.c:182
 hfsplus_free_extents+0x10d/0xa50 fs/hfsplus/extents.c:360
 hfsplus_file_truncate+0x735/0xb40 fs/hfsplus/extents.c:589
 hfsplus_setattr+0x1c3/0x280 fs/hfsplus/inode.c:269
 notify_change+0xb0d/0xe10 fs/attr.c:499
 do_truncate+0x19b/0x220 fs/open.c:66
 vfs_truncate+0x266/0x300 fs/open.c:112
 do_sys_truncate+0xe0/0x1a0 fs/open.c:135
 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: 0033:0x7fe03358f749
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:00007fe0343de038 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 00007fe0337e5fa0 RCX: 00007fe03358f749
RDX: 0000000000000000 RSI: 0200000080000000 RDI: 0000200000000080
RBP: 00007fe033613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe0337e6038 R14: 00007fe0337e5fa0 R15: 00007fff6bf83858
 </TASK>