UBSAN: array-index-out-of-bounds in dtSplitPage

Status: upstream: reported C repro on 2024/12/30 07:45
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+a0acccd8e6068831fd3b@syzkaller.appspotmail.com
First crash: 621d, last: 3d18h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/05/19 upstream (ToT) a5806cd506af C [report] KASAN: use-after-free Write in dtSplitPage
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 UBSAN: array-index-out-of-bounds in dtSplitPage origin:upstream 22 syz, C 167 3d17h 449d 0/2 upstream: reported C repro on 2025/06/20 22:01
upstream KASAN: slab-use-after-free Write in dtSplitPage prio:high jfs 22 syz, C inconclusive 8086 1d02h 636d 0/29 upstream: reported C repro on 2024/12/15 23:15
linux-5.15 UBSAN: array-index-out-of-bounds in dtSplitPage origin:upstream 22 syz, C error 144 9d02h 622d 0/3 upstream: reported C repro on 2024/12/29 06:57
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2026/07/28 05:13 2h48m bisect fix linux-6.1.y OK (0) job log log
2026/06/27 12:39 2h05m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
loop0: detected capacity change from 0 to 32768
==================================================================
BUG: KASAN: use-after-free in dtMoveEntry fs/jfs/jfs_dtree.c:3922 [inline]
BUG: KASAN: use-after-free in dtSplitPage+0x1a21/0x3160 fs/jfs/jfs_dtree.c:1561
Write of size 1 at addr ffff888023da9000 by task syz.0.17/4420

CPU: 1 PID: 4420 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 dtMoveEntry fs/jfs/jfs_dtree.c:3922 [inline]
 dtSplitPage+0x1a21/0x3160 fs/jfs/jfs_dtree.c:1561
 dtSplitUp fs/jfs/jfs_dtree.c:1092 [inline]
 dtInsert+0x106f/0x57e0 fs/jfs/jfs_dtree.c:871
 jfs_rename+0x89a/0x1910 fs/jfs/namei.c:1224
 vfs_rename+0xd57/0x10f0 fs/namei.c:4882
 do_renameat2+0x8ac/0xc80 fs/namei.c:5035
 __do_sys_rename fs/namei.c:5081 [inline]
 __se_sys_rename fs/namei.c:5079 [inline]
 __x64_sys_rename+0x82/0x90 fs/namei.c:5079
 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: 0033:0x7f5f0739e0d9
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:00007ffe7a818a08 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 00007f5f07625fa0 RCX: 00007f5f0739e0d9
RDX: 0000000000000000 RSI: 0000200000000f40 RDI: 00002000000003c0
RBP: 00007f5f07435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5f07625fac R14: 00007f5f07625fa0 R15: 00007f5f07625fa0
 </TASK>

Allocated by task 4315:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 __kasan_slab_alloc+0x6b/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x4b/0x490 mm/slab.h:737
 slab_alloc_node mm/slub.c:3359 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x18b/0x2f0 mm/slub.c:3383
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 proc_net_ns_init+0x4a/0x380 fs/proc/proc_net.c:361
 ops_init+0x360/0x5e0 net/core/net_namespace.c:138
 setup_net+0x4f2/0xbd0 net/core/net_namespace.c:336
 copy_net_ns+0x33e/0x5b0 net/core/net_namespace.c:508
 create_new_namespaces+0x3ce/0x700 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x116/0x160 kernel/nsproxy.c:226
 ksys_unshare+0x4f6/0x8e0 kernel/fork.c:3285
 __do_sys_unshare kernel/fork.c:3359 [inline]
 __se_sys_unshare kernel/fork.c:3357 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3357
 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

Freed by task 11:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free+0xf7/0x2a0 mm/slub.c:3709
 ops_exit_list net/core/net_namespace.c:172 [inline]
 cleanup_net+0x703/0xba0 net/core/net_namespace.c:640
 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff888023da9000
 which belongs to the cache proc_dir_entry of size 256
The buggy address is located 0 bytes inside of
 256-byte region [ffff888023da9000, ffff888023da9100)

The buggy address belongs to the physical page:
page:ffffea00008f6a40 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x23da9
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 0000000000000000 dead000000000122 ffff888140130780
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 4315, tgid 4315 (syz-executor), ts 88107957020, free_ts 88104809765
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560
 prep_new_page mm/page_alloc.c:2567 [inline]
 get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658
 alloc_slab_page+0x5d/0x180 mm/slub.c:1799
 allocate_slab mm/slub.c:1944 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:1997
 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3154
 __slab_alloc mm/slub.c:3240 [inline]
 slab_alloc_node mm/slub.c:3325 [inline]
 slab_alloc mm/slub.c:3367 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3374 [inline]
 kmem_cache_alloc+0x111/0x2f0 mm/slub.c:3383
 kmem_cache_zalloc include/linux/slab.h:689 [inline]
 proc_net_ns_init+0x4a/0x380 fs/proc/proc_net.c:361
 ops_init+0x360/0x5e0 net/core/net_namespace.c:138
 setup_net+0x4f2/0xbd0 net/core/net_namespace.c:336
 copy_net_ns+0x33e/0x5b0 net/core/net_namespace.c:508
 create_new_namespaces+0x3ce/0x700 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x116/0x160 kernel/nsproxy.c:226
 ksys_unshare+0x4f6/0x8e0 kernel/fork.c:3285
 __do_sys_unshare kernel/fork.c:3359 [inline]
 __se_sys_unshare kernel/fork.c:3357 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3357
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1487 [inline]
 free_pcp_prepare mm/page_alloc.c:1537 [inline]
 free_unref_page_prepare+0x8e5/0x9e0 mm/page_alloc.c:3414
 free_unref_page+0x2e/0x3f0 mm/page_alloc.c:3509
 __vunmap+0x874/0xa40 mm/vmalloc.c:2726
 free_work+0x56/0x80 mm/vmalloc.c:97
 process_one_work+0x8ab/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaf5/0x12a0 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff888023da8f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888023da8f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888023da9000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888023da9080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888023da9100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================

Crashes (294):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/17 08:08 linux-6.1.y e4f7d8be268e 746171ee .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: use-after-free Write in dtSplitPage
2025/08/23 05:37 linux-6.1.y 0bc96de781b4 bf27483f .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in dtSplitPage
2025/05/12 10:04 linux-6.1.y 02b72ccb5f9d 77908e5f .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: use-after-free Write in dtSplitPage
2025/12/01 20:51 linux-6.1.y f6e38ae624cf d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/08/17 08:07 linux-6.1.y e4f7d8be268e 746171ee .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Write in dtSplitPage
2025/04/21 19:27 linux-6.1.y 420102835862 2a20f901 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan UBSAN: array-index-out-of-bounds in dtSplitPage
2024/12/30 07:45 linux-6.1.y 563edd786f0a d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan UBSAN: array-index-out-of-bounds in dtSplitPage
2026/09/09 12:04 linux-6.1.y cf82dcca9634 8387c273 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in dtSplitPage
2026/08/28 01:11 linux-6.1.y 79a9660d699e 69a01293 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in dtSplitPage
2026/08/17 07:03 linux-6.1.y e4f7d8be268e 746171ee .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Write in dtSplitPage
2026/04/07 05:07 linux-6.1.y 1989cd3d56e2 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/24 19:46 linux-6.1.y 779f9571ac3e 96b1aa46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/21 22:03 linux-6.1.y 779f9571ac3e 6e7b5511 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/26 09:22 linux-6.1.y cd9b81672742 55756628 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/25 17:50 linux-6.1.y cd9b81672742 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/28 09:25 linux-6.1.y dcbcab9d7079 4c36e7e5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/25 05:38 linux-6.1.y dcbcab9d7079 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/23 18:21 linux-6.1.y dcbcab9d7079 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in dtSplitPage
2026/05/23 11:03 linux-6.1.y c27210688955 c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/18 17:38 linux-6.1.y c27210688955 55156e84 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/14 13:55 linux-6.1.y ad16b162f21d 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/10 07:09 linux-6.1.y 128a674368bf 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/05 07:10 linux-6.1.y 4931e0e1673d a898ba9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/03 15:48 linux-6.1.y 4931e0e1673d a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/05/01 09:47 linux-6.1.y 4931e0e1673d 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/23 10:18 linux-6.1.y 7c87defbd336 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/20 13:30 linux-6.1.y 7c87defbd336 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/16 22:20 linux-6.1.y 8e8fc038cad5 4743f87d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/13 22:02 linux-6.1.y 8e8fc038cad5 9530ccf9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/13 07:56 linux-6.1.y 8e8fc038cad5 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/12 18:10 linux-6.1.y 8e8fc038cad5 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/11 09:50 linux-6.1.y 1989cd3d56e2 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/04/06 11:25 linux-6.1.y 1989cd3d56e2 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/03/30 07:58 linux-6.1.y 1989cd3d56e2 b5ceaad2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/03/24 12:12 linux-6.1.y f2ddafa93a25 baf8bf12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/03/21 02:16 linux-6.1.y f2ddafa93a25 ac6f1dff .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/03/08 18:06 linux-6.1.y f2ddafa93a25 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/03/07 12:16 linux-6.1.y f2ddafa93a25 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/03/06 10:16 linux-6.1.y f2ddafa93a25 31e9c887 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/16 02:30 linux-6.1.y 8ce36b2849ef 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/15 14:55 linux-6.1.y 8ce36b2849ef 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/14 20:23 linux-6.1.y 8ce36b2849ef 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/06 09:23 linux-6.1.y cd9b81672742 f03c4191 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/02/01 16:56 linux-6.1.y cd9b81672742 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/28 09:43 linux-6.1.y cd9b81672742 3029c699 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/26 06:23 linux-6.1.y cd9b81672742 55756628 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/25 15:46 linux-6.1.y cd9b81672742 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/25 09:44 linux-6.1.y cd9b81672742 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/23 00:48 linux-6.1.y cd9b81672742 82c9c083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/23 00:46 linux-6.1.y cd9b81672742 82c9c083 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/18 12:15 linux-6.1.y cd9b81672742 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
2026/01/15 21:07 linux-6.1.y bec0e10ee67e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in dtSplitPage
* Struck through repros no longer work on HEAD.