[syzbot] [ocfs2?] possible deadlock in __ocfs2_reflink

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3b5f4b83c4ab Merge tag 'for-7.2-rc5-tag' of git://git.kern..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178e72a9580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c05be6c9b0d36cb9
dashboard link: https://syzkaller.appspot.com/bug?extid=7845c7b269ac2d175080
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-3b5f4b83.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bc8222697dfb/vmlinux-3b5f4b83.xz
kernel image: https://storage.googleapis.com/syzbot-assets/24ab3896211c/bzImage-3b5f4b83.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7845c7...@syzkaller.appspotmail.com


======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.0/5337 is trying to acquire lock:
ffff888044266ba0 (&sb->s_type->i_mutex_key#24/2){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
ffff888044266ba0 (&sb->s_type->i_mutex_key#24/2){+.+.}-{4:4}, at: __ocfs2_reflink+0xace/0x16f0 fs/ocfs2/refcounttree.c:4174

but task is already holding lock:
ffff88804426a258 (&oi->ip_alloc_sem){++++}-{4:4}, at: ocfs2_reflink+0x4d2/0x920 fs/ocfs2/refcounttree.c:4272

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&oi->ip_alloc_sem){++++}-{4:4}:
down_read+0x4a/0x330 kernel/locking/rwsem.c:1574
ocfs2_inode_lock_for_extent_tree+0xd6/0x190 fs/ocfs2/file.c:2222
ocfs2_prepare_inode_for_write fs/ocfs2/file.c:2278 [inline]
ocfs2_file_write_iter+0x6d5/0x1f10 fs/ocfs2/file.c:2463
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x612/0xba0 fs/read_write.c:687
ksys_write+0x150/0x270 fs/read_write.c:739
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}:
down_write+0x96/0x200 kernel/locking/rwsem.c:1631
inode_lock include/linux/fs.h:1024 [inline]
vfs_rename+0x6e3/0xef0 fs/namei.c:-1
filename_renameat2+0x533/0x9a0 fs/namei.c:6192
__do_sys_renameat2 fs/namei.c:6221 [inline]
__se_sys_renameat2+0x5a/0x2c0 fs/namei.c:6216
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sb->s_type->i_mutex_key#24/2){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
down_write_nested+0x9d/0x210 kernel/locking/rwsem.c:1757
inode_lock_nested include/linux/fs.h:1069 [inline]
__ocfs2_reflink+0xace/0x16f0 fs/ocfs2/refcounttree.c:4174
ocfs2_reflink+0x4eb/0x920 fs/ocfs2/refcounttree.c:4273
ocfs2_vfs_reflink+0x338/0x450 fs/ocfs2/refcounttree.c:4399
ocfs2_reflink_ioctl+0x3a0/0x450 fs/ocfs2/refcounttree.c:4439
ocfs2_ioctl+0x5b5/0x7e0 fs/ocfs2/ioctl.c:920
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
&sb->s_type->i_mutex_key#24/2 --> &sb->s_type->i_mutex_key#24 --> &oi->ip_alloc_sem

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&oi->ip_alloc_sem);
lock(&sb->s_type->i_mutex_key#24);
lock(&oi->ip_alloc_sem);
lock(&sb->s_type->i_mutex_key#24/2);

*** DEADLOCK ***

5 locks held by syz.0.0/5337:
#0: ffff888032e58450 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:494
#1: ffff88804425a5a0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1069 [inline]
#1: ffff88804425a5a0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2918 [inline]
#1: ffff88804425a5a0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2942 [inline]
#1: ffff88804425a5a0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370 fs/namei.c:4955
#2: ffff88804426a5a0 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
#2: ffff88804426a5a0 (&sb->s_type->i_mutex_key#24){+.+.}-{4:4}, at: ocfs2_vfs_reflink+0x2f8/0x450 fs/ocfs2/refcounttree.c:4396
#3: ffff88804426a2e8 (&oi->ip_xattr_sem){++++}-{4:4}, at: ocfs2_reflink+0x4c3/0x920 fs/ocfs2/refcounttree.c:4271
#4: ffff88804426a258 (&oi->ip_alloc_sem){++++}-{4:4}, at: ocfs2_reflink+0x4d2/0x920 fs/ocfs2/refcounttree.c:4272

stack backtrace:
CPU: 0 UID: 0 PID: 5337 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
down_write_nested+0x9d/0x210 kernel/locking/rwsem.c:1757
inode_lock_nested include/linux/fs.h:1069 [inline]
__ocfs2_reflink+0xace/0x16f0 fs/ocfs2/refcounttree.c:4174
ocfs2_reflink+0x4eb/0x920 fs/ocfs2/refcounttree.c:4273
ocfs2_vfs_reflink+0x338/0x450 fs/ocfs2/refcounttree.c:4399
ocfs2_reflink_ioctl+0x3a0/0x450 fs/ocfs2/refcounttree.c:4439
ocfs2_ioctl+0x5b5/0x7e0 fs/ocfs2/ioctl.c:920
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f690739de99
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f69037b2fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f6907626180 RCX: 00007f690739de99
RDX: 00002000000001c0 RSI: 0000000040186f04 RDI: 0000000000000004
RBP: 00007f6907433eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6907626218 R14: 00007f6907626180 R15: 00007ffc041371e8
</TASK>


---
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