[v6.6] possible deadlock in ocfs2_try_remove_refcount_tree

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syzbot

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Jun 16, 2025, 3:34:29 PM6/16/25

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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=11641e82580000
kernel config: https://syzkaller.appspot.com/x/.config?x=486bade17c8c30b9
dashboard link: https://syzkaller.appspot.com/bug?extid=495f525466a86b5987f8
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+495f52...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
ocfs2: Mounting device (7,0) on (node local, slot 0) with ordered data mode.
======================================================
WARNING: possible circular locking dependency detected
6.6.93-syzkaller #0 Not tainted
------------------------------------------------------
syz.0.8670/6142 is trying to acquire lock:
ffff88805bd0b120 (&ocfs2_file_ip_alloc_sem_key){++++}-{3:3}, at: ocfs2_try_remove_refcount_tree+0xb7/0x320 fs/ocfs2/refcounttree.c:932

but task is already holding lock:
ffff88805bd0b1b8 (&oi->ip_xattr_sem){++++}-{3:3}, at: ocfs2_try_remove_refcount_tree+0xa5/0x320 fs/ocfs2/refcounttree.c:931

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #4 (&oi->ip_xattr_sem){++++}-{3:3}:
down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
ocfs2_init_acl+0x2fa/0x720 fs/ocfs2/acl.c:366
ocfs2_mknod+0x12e5/0x20f0 fs/ocfs2/namei.c:410
ocfs2_create+0x196/0x410 fs/ocfs2/namei.c:674
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

-> #3 (jbd2_handle){++++}-{0:0}:
start_this_handle+0x1e9d/0x20c0 fs/jbd2/transaction.c:448
jbd2__journal_start+0x2bb/0x5b0 fs/jbd2/transaction.c:505
jbd2_journal_start+0x2a/0x40 fs/jbd2/transaction.c:544
ocfs2_start_trans+0x376/0x6c0 fs/ocfs2/journal.c:374
ocfs2_mknod+0xe47/0x20f0 fs/ocfs2/namei.c:361
ocfs2_create+0x196/0x410 fs/ocfs2/namei.c:674
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

-> #2 (&journal->j_trans_barrier){.+.+}-{3:3}:
down_read+0x46/0x2e0 kernel/locking/rwsem.c:1520
ocfs2_start_trans+0x36a/0x6c0 fs/ocfs2/journal.c:372
ocfs2_mknod+0xe47/0x20f0 fs/ocfs2/namei.c:361
ocfs2_create+0x196/0x410 fs/ocfs2/namei.c:674
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

-> #1 (sb_internal#4){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1633 [inline]
sb_start_intwrite include/linux/fs.h:1755 [inline]
ocfs2_start_trans+0x26b/0x6c0 fs/ocfs2/journal.c:370
ocfs2_write_begin_inline fs/ocfs2/aops.c:1481 [inline]
ocfs2_try_to_write_inline_data fs/ocfs2/aops.c:1584 [inline]
ocfs2_write_begin_nolock+0x1c91/0x4190 fs/ocfs2/aops.c:1670
ocfs2_write_begin+0x1bc/0x310 fs/ocfs2/aops.c:1904
generic_perform_write+0x2fb/0x5b0 mm/filemap.c:4016
ocfs2_file_write_iter+0x1582/0x1d00 fs/ocfs2/file.c:2468
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 (&ocfs2_file_ip_alloc_sem_key){++++}-{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
down_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
ocfs2_try_remove_refcount_tree+0xb7/0x320 fs/ocfs2/refcounttree.c:932
ocfs2_xattr_set+0x596/0x11f0 fs/ocfs2/xattr.c:3669
ocfs2_set_acl+0x4e1/0x590 fs/ocfs2/acl.c:254
ocfs2_iop_set_acl+0x1ab/0x2a0 fs/ocfs2/acl.c:286
set_posix_acl fs/posix_acl.c:956 [inline]
vfs_set_acl+0x803/0xa60 fs/posix_acl.c:1135
do_setxattr fs/xattr.c:627 [inline]
path_setxattr+0x39f/0x550 fs/xattr.c:659
__do_sys_setxattr fs/xattr.c:677 [inline]
__se_sys_setxattr fs/xattr.c:673 [inline]
__x64_sys_setxattr+0xbb/0xd0 fs/xattr.c:673
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:

Chain exists of:
&ocfs2_file_ip_alloc_sem_key --> jbd2_handle --> &oi->ip_xattr_sem

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&oi->ip_xattr_sem);
lock(jbd2_handle);
lock(&oi->ip_xattr_sem);
lock(&ocfs2_file_ip_alloc_sem_key);

*** DEADLOCK ***

3 locks held by syz.0.8670/6142:
#0: ffff8880416f2418 (sb_writers#23){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:403
#1: ffff88805bd0b498 (&type->i_mutex_dir_key#13){++++}-{3:3}, at: inode_lock include/linux/fs.h:804 [inline]
#1: ffff88805bd0b498 (&type->i_mutex_dir_key#13){++++}-{3:3}, at: vfs_set_acl+0x37a/0xa60 fs/posix_acl.c:1116
#2: ffff88805bd0b1b8 (&oi->ip_xattr_sem){++++}-{3:3}, at: ocfs2_try_remove_refcount_tree+0xa5/0x320 fs/ocfs2/refcounttree.c:931

stack backtrace:
CPU: 0 PID: 6142 Comm: syz.0.8670 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
down_write+0x97/0x1f0 kernel/locking/rwsem.c:1573
ocfs2_try_remove_refcount_tree+0xb7/0x320 fs/ocfs2/refcounttree.c:932
ocfs2_xattr_set+0x596/0x11f0 fs/ocfs2/xattr.c:3669
ocfs2_set_acl+0x4e1/0x590 fs/ocfs2/acl.c:254
ocfs2_iop_set_acl+0x1ab/0x2a0 fs/ocfs2/acl.c:286
set_posix_acl fs/posix_acl.c:956 [inline]
vfs_set_acl+0x803/0xa60 fs/posix_acl.c:1135
do_setxattr fs/xattr.c:627 [inline]
path_setxattr+0x39f/0x550 fs/xattr.c:659
__do_sys_setxattr fs/xattr.c:677 [inline]
__se_sys_setxattr fs/xattr.c:673 [inline]
__x64_sys_setxattr+0xbb/0xd0 fs/xattr.c:673
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: 0033:0x7f45dd18e929
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:00007f45ddf17038 EFLAGS: 00000246 ORIG_RAX: 00000000000000bc
RAX: ffffffffffffffda RBX: 00007f45dd3b5fa0 RCX: 00007f45dd18e929
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000200000002a00
RBP: 00007f45dd210b39 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f45dd3b5fa0 R15: 00007ffeed383378
</TASK>

---
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syzbot

unread,

Jun 21, 2025, 6:42:26 PM6/21/25

to syzkaller...@googlegroups.com

syzbot has found a reproducer for the following issue on:

HEAD commit: 6282921b6825 Linux 6.6.94
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=176d330c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=96da6b2210cda427

dashboard link: https://syzkaller.appspot.com/bug?extid=495f525466a86b5987f8
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=153ef30c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a3bf0d8e22b2/disk-6282921b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d1d442f782d0/vmlinux-6282921b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a8378f4b7e1b/bzImage-6282921b.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/fa456d97fdca/mount_0.gz
fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=100bc182580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+495f52...@syzkaller.appspotmail.com

ocfs2: Mounting device (7,3) on (node local, slot 0) with writeback data mode.

======================================================
WARNING: possible circular locking dependency detected

6.6.94-syzkaller #0 Not tainted
------------------------------------------------------
syz.3.88/6301 is trying to acquire lock:
ffff88807248ea20 (&ocfs2_file_ip_alloc_sem_key){++++}-{3:3}, at: ocfs2_try_remove_refcount_tree+0xb7/0x320 fs/ocfs2/refcounttree.c:932

but task is already holding lock:

ffff88807248eab8 (&oi->ip_xattr_sem){++++}-{3:3}, at: ocfs2_try_remove_refcount_tree+0xa5/0x320 fs/ocfs2/refcounttree.c:931