possible deadlock in ocfs2_lock_refcount_tree (2)

Status: upstream: reported on 2026/05/11 00:20
Reported-by: syzbot+1698551c43bd8a774aa5@syzkaller.appspotmail.com
First crash: 77d, last: 3d22h
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream possible deadlock in ocfs2_lock_refcount_tree (4) prio:high ocfs2 4 20 42d 94d 0/29 upstream: reported on 2026/04/24 03:20
linux-5.15 possible deadlock in ocfs2_lock_refcount_tree 4 58 321d 680d 0/3 auto-obsoleted due to no activity on 2025/12/04 20:56
linux-5.15 possible deadlock in ocfs2_lock_refcount_tree (3) 4 2 31d 56d 0/3 upstream: reported on 2026/06/01 02:21
upstream possible deadlock in ocfs2_lock_refcount_tree (3) ocfs2 4 1 310d 306d 0/29 auto-obsoleted due to no activity on 2025/12/28 08:20
linux-6.1 possible deadlock in ocfs2_lock_refcount_tree 4 97 184d 622d 0/3 auto-obsoleted due to no activity on 2026/04/03 15:33
upstream possible deadlock in ocfs2_lock_refcount_tree ocfs2 4 5 672d 688d 0/29 auto-obsoleted due to no activity on 2025/01/01 02:27
upstream possible deadlock in ocfs2_lock_refcount_tree (2) ocfs2 4 5 515d 563d 0/29 auto-obsoleted due to no activity on 2025/06/06 14:54
linux-5.15 possible deadlock in ocfs2_lock_refcount_tree (2) 4 3 202d 221d 0/3 auto-obsoleted due to no activity on 2026/04/15 05:38

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.353/5728 is trying to acquire lock:
ffff88801fe72098 (&new->rf_sem){+.+.}-{3:3}, at: __ocfs2_lock_refcount_tree fs/ocfs2/refcounttree.c:428 [inline]
ffff88801fe72098 (&new->rf_sem){+.+.}-{3:3}, at: ocfs2_lock_refcount_tree+0x1aa/0x9d0 fs/ocfs2/refcounttree.c:463

but task is already holding lock:
ffff8880725c8660 (&ocfs2_file_ip_alloc_sem_key){++++}-{3:3}, at: ocfs2_inode_lock_for_extent_tree+0x72/0x190 fs/ocfs2/file.c:2208

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&ocfs2_file_ip_alloc_sem_key){++++}-{3:3}
:
       down_read+0x42/0x2d0 kernel/locking/rwsem.c:1520
       ocfs2_read_virt_blocks+0x266/0x980 fs/ocfs2/extent_map.c:984
       ocfs2_read_dir_block fs/ocfs2/dir.c:508 [inline]
       ocfs2_find_entry_el fs/ocfs2/dir.c:715 [inline]
       ocfs2_find_entry+0x3a8/0x2080 fs/ocfs2/dir.c:1091
       ocfs2_find_files_on_disk+0x102/0x390 fs/ocfs2/dir.c:1995
       ocfs2_lookup_ino_from_name+0x4f/0xf0 fs/ocfs2/dir.c:2017
       _ocfs2_get_system_file_inode fs/ocfs2/sysfile.c:136 [inline]
       ocfs2_get_system_file_inode+0x34d/0x820 fs/ocfs2/sysfile.c:112
       ocfs2_init_global_system_inodes+0x315/0x6e0 fs/ocfs2/super.c:457
       ocfs2_initialize_super fs/ocfs2/super.c:2253 [inline]
       ocfs2_fill_super+0x2b5a/0x5020 fs/ocfs2/super.c:994
       mount_bdev+0x28a/0x3c0 fs/super.c:1443
       legacy_get_tree+0xe6/0x180 fs/fs_context.c:632
       vfs_get_tree+0x88/0x270 fs/super.c:1573
       do_new_mount+0x247/0xa40 fs/namespace.c:3078
       do_mount fs/namespace.c:3421 [inline]
       __do_sys_mount fs/namespace.c:3629 [inline]
       __se_sys_mount+0x2e3/0x3d0 fs/namespace.c:3606
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&osb->system_file_mutex){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
       ocfs2_get_system_file_inode+0x1a2/0x820 fs/ocfs2/sysfile.c:101
       ocfs2_reserve_suballoc_bits+0x12e/0x4810 fs/ocfs2/suballoc.c:798
       ocfs2_reserve_new_metadata_blocks+0x412/0x9a0 fs/ocfs2/suballoc.c:1000
       ocfs2_add_refcount_flag+0x398/0xf10 fs/ocfs2/refcounttree.c:3683
       ocfs2_reflink_remap_extent fs/ocfs2/refcounttree.c:4563 [inline]
       ocfs2_reflink_remap_blocks+0xd66/0x1aa0 fs/ocfs2/refcounttree.c:4690
       ocfs2_remap_file_range+0x4a7/0x740 fs/ocfs2/file.c:2703
       vfs_copy_file_range+0xd93/0x14f0 fs/read_write.c:1518
       __do_sys_copy_file_range fs/read_write.c:1596 [inline]
       __se_sys_copy_file_range+0x320/0x470 fs/read_write.c:1559
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (&new->rf_sem){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3830 [inline]
       __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
       lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
       down_write+0x36/0x60 kernel/locking/rwsem.c:1573
       __ocfs2_lock_refcount_tree fs/ocfs2/refcounttree.c:428 [inline]
       ocfs2_lock_refcount_tree+0x1aa/0x9d0 fs/ocfs2/refcounttree.c:463
       ocfs2_refcount_cow_hunk fs/ocfs2/refcounttree.c:3415 [inline]
       ocfs2_refcount_cow+0x585/0xcf0 fs/ocfs2/refcounttree.c:3476
       ocfs2_prepare_inode_for_write fs/ocfs2/file.c:2340 [inline]
       ocfs2_file_write_iter+0xf4d/0x1fc0 fs/ocfs2/file.c:2451
       do_iter_readv_writev fs/read_write.c:-1 [inline]
       do_iter_write+0x638/0xb10 fs/read_write.c:861
       iter_file_splice_write+0x6be/0xcf0 fs/splice.c:685
       do_splice_from fs/splice.c:763 [inline]
       direct_splice_actor+0xe1/0x130 fs/splice.c:950
       splice_direct_to_actor+0x4b8/0xbd0 fs/splice.c:896
       do_splice_direct+0x1ce/0x2f0 fs/splice.c:1002
       do_sendfile+0x51b/0xe20 fs/read_write.c:1255
       __do_sys_sendfile64 fs/read_write.c:1323 [inline]
       __se_sys_sendfile64+0x141/0x1a0 fs/read_write.c:1309
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  &new->rf_sem --> &osb->system_file_mutex --> &ocfs2_file_ip_alloc_sem_key

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ocfs2_file_ip_alloc_sem_key);
                               lock(&osb->system_file_mutex);
                               lock(&ocfs2_file_ip_alloc_sem_key);
  lock(&new->rf_sem);

 *** DEADLOCK ***

3 locks held by syz.2.353/5728:
 #0: ffff888027746460 (sb_writers#14){.+.+}-{0:0}, at: do_sendfile+0x4f6/0xe20 fs/read_write.c:1254
 #1: ffff8880725c89c8 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff8880725c89c8 (&sb->s_type->i_mutex_key#21){+.+.}-{3:3}, at: ocfs2_file_write_iter+0x45a/0x1fc0 fs/ocfs2/file.c:2399
 #2: ffff8880725c8660 (&ocfs2_file_ip_alloc_sem_key){++++}-{3:3}, at: ocfs2_inode_lock_for_extent_tree+0x72/0x190 fs/ocfs2/file.c:2208

stack backtrace:
CPU: 1 PID: 5728 Comm: syz.2.353 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3830 [inline]
 __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5676
 down_write+0x36/0x60 kernel/locking/rwsem.c:1573
 __ocfs2_lock_refcount_tree fs/ocfs2/refcounttree.c:428 [inline]
 ocfs2_lock_refcount_tree+0x1aa/0x9d0 fs/ocfs2/refcounttree.c:463
 ocfs2_refcount_cow_hunk fs/ocfs2/refcounttree.c:3415 [inline]
 ocfs2_refcount_cow+0x585/0xcf0 fs/ocfs2/refcounttree.c:3476
 ocfs2_prepare_inode_for_write fs/ocfs2/file.c:2340 [inline]
 ocfs2_file_write_iter+0xf4d/0x1fc0 fs/ocfs2/file.c:2451
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x638/0xb10 fs/read_write.c:861
 iter_file_splice_write+0x6be/0xcf0 fs/splice.c:685
 do_splice_from fs/splice.c:763 [inline]
 direct_splice_actor+0xe1/0x130 fs/splice.c:950
 splice_direct_to_actor+0x4b8/0xbd0 fs/splice.c:896
 do_splice_direct+0x1ce/0x2f0 fs/splice.c:1002
 do_sendfile+0x51b/0xe20 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1323 [inline]
 __se_sys_sendfile64+0x141/0x1a0 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f3d36d9de99
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:00007f3d37ba4028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f3d37025fa0 RCX: 00007f3d36d9de99
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005
RBP: 00007f3d36e33eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000fffe82 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3d37026038 R14: 00007f3d37025fa0 R15: 00007ffe66edd4e8
 </TASK>

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/23 05:20 linux-6.1.y 090666d3cc90 881ce5c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in ocfs2_lock_refcount_tree
2026/06/20 05:42 linux-6.1.y fdb6fcb41cc7 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in ocfs2_lock_refcount_tree
2026/06/26 02:38 linux-6.1.y fdb6fcb41cc7 7ff32d8b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
2026/06/04 18:38 linux-6.1.y 228da13e907e 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
2026/06/04 18:30 linux-6.1.y 228da13e907e 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
2026/06/04 18:04 linux-6.1.y 228da13e907e 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
2026/06/04 18:02 linux-6.1.y 228da13e907e 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
2026/06/04 18:00 linux-6.1.y 228da13e907e 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
2026/05/11 00:20 linux-6.1.y 128a674368bf 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 possible deadlock in ocfs2_lock_refcount_tree
* Struck through repros no longer work on HEAD.