syzbot


WARNING in gid_table_release_one (3)

Status: upstream: reported C repro on 2025/05/13 11:35
Subsystems: rdma
[Documentation on labels]
Reported-by: syzbot+b0da83a6c0e2e2bddbd4@syzkaller.appspotmail.com
First crash: 214d, last: 10h41m
Cause bisection: introduced by (bisect log) :
commit a92fbeac7e94a420b55570c10fe1b90e64da4025
Author: Leon Romanovsky <leonro@nvidia.com>
Date: Tue May 28 12:52:51 2024 +0000

  RDMA/cache: Release GID table even if leak is detected

Crash: WARNING in gid_table_release_one (log)
Repro: C syz .config
  
Discussions (9)
Title Replies (including bot) Last reply
[syzbot] [rdma?] WARNING in gid_table_release_one (3) 12 (42) 2025/12/07 15:13
[syzbot] Monthly rdma report (Nov 2025) 0 (1) 2025/11/24 07:46
Re: [syzbot] [rdma?] WARNING in gid_table_release_one (3) 1 (1) 2025/11/06 21:08
Re: [syzbot] [rdma?] WARNING in gid_table_release_one (3) 5 (5) 2025/11/06 00:44
[syzbot] Monthly rdma report (Oct 2025) 1 (2) 2025/10/23 19:05
Re: [syzbot] [rdma?] WARNING in gid_table_release_one (3) 1 (1) 2025/09/16 16:12
[syzbot] Monthly rdma report (Aug 2025) 0 (1) 2025/08/21 12:33
[syzbot] Monthly rdma report (Jul 2025) 0 (1) 2025/07/21 07:58
[syzbot] Monthly rdma report (Jun 2025) 3 (4) 2025/06/20 15:56
Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 WARNING in gid_table_release_one origin:upstream -1 syz 40 1h59m 211d 0/3 upstream: reported syz repro on 2025/05/12 20:58
linux-6.1 WARNING in gid_table_release_one -1 1 479d 479d 0/3 auto-obsoleted due to no activity on 2024/11/25 05:33
upstream WARNING in gid_table_release_one (2) rdma -1 1 467d 463d 28/29 fixed on 2024/10/24 03:35
upstream WARNING in gid_table_release_one rdma -1 12 530d 537d 0/29 auto-obsoleted due to no activity on 2024/08/06 20:20
linux-6.1 WARNING in gid_table_release_one (3) origin:upstream -1 syz 10 2d03h 39d 0/3 upstream: reported syz repro on 2025/10/31 21:06
linux-6.6 WARNING in gid_table_release_one -1 21 48m 171d 0/2 upstream: reported on 2025/06/21 11:54
linux-6.1 WARNING in gid_table_release_one (2) -1 3 194d 214d 0/3 auto-obsoleted due to no activity on 2025/09/06 20:49
Last patch testing requests (36)
Created Duration User Patch Repo Result
2025/12/07 15:13 52m cmeiohas@nvidia.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci OK log
2025/12/07 13:20 27m cmeiohas@nvidia.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci error
2025/12/07 13:18 11m cmeiohas@nvidia.com patch git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci error
2025/11/06 18:57 19m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/11/06 01:45 2h15m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/11/06 00:33 37m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/11/05 18:33 50m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/11/05 17:24 1h07m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one OK log
2025/11/05 16:44 18m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/11/04 21:03 27m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one OK log
2025/11/04 18:47 2h06m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one OK log
2025/09/25 19:59 29m retest repro linux-next report log
2025/09/18 04:27 27m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one OK log
2025/09/16 21:47 32m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one OK log
2025/09/16 21:16 21m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/16 15:21 26m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one OK log
2025/09/16 05:02 34m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/16 01:02 57m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/15 22:49 2h21m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/15 21:34 38m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/13 07:25 39m hdanton@sina.com patch linux-next OK log
2025/09/13 01:25 18m hdanton@sina.com patch linux-next report log
2025/09/12 21:44 19m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/12 20:50 25m yanjun.zhu@linux.dev https://github.com/zhuyj/linux.git v6.17_fix_gid_table_release_one report log
2025/09/12 09:42 37m hdanton@sina.com patch linux-next report log
2025/09/12 08:34 0m hdanton@sina.com patch linux-next error
2025/09/12 03:39 14m hdanton@sina.com patch linux-next error
2025/08/17 16:57 20m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/08/03 13:20 31m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/08/03 13:20 36m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/08/03 13:20 20m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/08/03 13:20 20m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/08/03 13:20 19m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/05/24 06:40 19m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/05/24 06:40 20m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log
2025/05/24 06:40 21m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci report log

Sample crash report:
------------[ cut here ]------------
GID entry ref leak for dev syz1 index 2 ref=615
WARNING: drivers/infiniband/core/cache.c:809 at release_gid_table drivers/infiniband/core/cache.c:806 [inline], CPU#0: kworker/u8:2/36
WARNING: drivers/infiniband/core/cache.c:809 at gid_table_release_one+0x346/0x4d0 drivers/infiniband/core/cache.c:886, CPU#0: kworker/u8:2/36
Modules linked in:
CPU: 0 UID: 0 PID: 36 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: ib-unreg-wq ib_unregister_work
RIP: 0010:release_gid_table drivers/infiniband/core/cache.c:806 [inline]
RIP: 0010:gid_table_release_one+0x346/0x4d0 drivers/infiniband/core/cache.c:886
Code: e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 75 3d 41 8b 0e 48 c7 c7 a0 43 91 8c 4c 89 e6 44 89 fa e8 fb 67 f5 f8 90 <0f> 0b 90 90 e9 e3 fe ff ff 44 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c
RSP: 0018:ffffc90000ac7908 EFLAGS: 00010246
RAX: 621d731dcb27e200 RBX: ffff88806241b8d8 RCX: ffff888141289e40
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: 1ffff1100c48371b R08: ffff8880b8724253 R09: 1ffff110170e484a
R10: dffffc0000000000 R11: ffffed10170e484b R12: ffff888027503e00
R13: ffff88806241b800 R14: ffff8880289a2400 R15: 0000000000000002
FS:  0000000000000000(0000) GS:ffff8881259f0000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555569847588 CR3: 00000000338c8000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ib_device_release+0xd2/0x1c0 drivers/infiniband/core/device.c:509
 device_release+0x99/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x228/0x480 lib/kobject.c:737
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x47c/0x820 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (288):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/11 15:33 linux-next 5f540c4aade9 fdeaa69b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in gid_table_release_one
2025/12/06 03:57 linux-next 6987d58a9cbc d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce WARNING in gid_table_release_one
2025/05/10 02:44 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c32f8dc5aaf9 bb813bcc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/05/10 01:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c32f8dc5aaf9 bb813bcc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/05/09 23:47 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c32f8dc5aaf9 bb813bcc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/05/09 22:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c32f8dc5aaf9 bb813bcc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/05/09 20:57 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c32f8dc5aaf9 bb813bcc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/05/09 19:31 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci c32f8dc5aaf9 bb813bcc .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/12/09 15:25 upstream cb015814f8b6 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/09 13:04 upstream a110f942672c d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/09 06:31 upstream a110f942672c d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/09 06:22 upstream a110f942672c d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in gid_table_release_one
2025/12/09 04:54 upstream a110f942672c d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/12/08 22:02 upstream c2f2b01b74be d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/08 18:25 upstream c2f2b01b74be d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/08 16:34 upstream c2f2b01b74be d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/12/08 15:11 upstream c2f2b01b74be d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/08 14:00 upstream c2f2b01b74be d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/08 13:44 upstream c2f2b01b74be d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/08 02:12 upstream 37bb2e7217b0 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in gid_table_release_one
2025/12/07 22:52 upstream 37bb2e7217b0 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in gid_table_release_one
2025/12/07 18:19 upstream 37bb2e7217b0 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/07 03:45 upstream 50471f8b7371 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/12/07 02:32 upstream 416f99c3b16f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/07 01:10 upstream 416f99c3b16f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/12/07 00:04 upstream 416f99c3b16f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/12/06 23:48 upstream 416f99c3b16f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/06 22:13 upstream 416f99c3b16f d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/12/06 11:10 upstream 51d90a15fedf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/06 08:46 upstream 51d90a15fedf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/06 06:37 upstream 51d90a15fedf d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/05 22:09 upstream 2061f18ad76e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/05 19:56 upstream 2061f18ad76e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/05 17:41 upstream 2061f18ad76e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/04 17:59 upstream 559e608c4655 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root WARNING in gid_table_release_one
2025/12/04 12:50 upstream 559e608c4655 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root WARNING in gid_table_release_one
2025/11/13 11:11 upstream e927c520e1ba 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root WARNING in gid_table_release_one
2025/11/24 16:00 upstream ac3fd01e4c1e bf6fe8fe .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root WARNING in gid_table_release_one
2025/11/15 02:42 upstream 7a0892d2836e f7988ea4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream WARNING in gid_table_release_one
2025/12/09 02:44 upstream a110f942672c d1b870e1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/12/06 18:09 upstream 416f99c3b16f d1b870e1 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/23 17:25 upstream d13f3ac64efb 4fb8ef37 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/23 11:41 upstream d13f3ac64efb 4fb8ef37 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/15 21:17 upstream f824272b6e3f f7988ea4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/14 21:59 upstream 6da43bbeb691 6d98c1c8 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/14 21:57 upstream 6da43bbeb691 6d98c1c8 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/13 18:37 upstream 2ccec5944606 07e030de .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/13 02:32 upstream 24172e0d7990 07e030de .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/12 14:40 upstream 24172e0d7990 07e030de .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/12 10:04 upstream 24172e0d7990 4e1406b4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/11 20:37 upstream 4427259cc7f7 4e1406b4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/11 18:22 upstream 4427259cc7f7 4e1406b4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/09 01:38 upstream 7bb4d6512545 4e1406b4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/08 19:24 upstream e811c33b1f13 4e1406b4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/11/08 12:04 upstream e811c33b1f13 4e1406b4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 WARNING in gid_table_release_one
2025/10/01 00:18 upstream 30d4efb2f5a5 65a0eece .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64-mte WARNING in gid_table_release_one
2025/05/30 04:30 upstream e0797d3b91de 3d2f584d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu2-arm64 WARNING in gid_table_release_one
2025/12/09 07:49 linux-next c75caf76ed86 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in gid_table_release_one
2025/12/06 18:38 linux-next 6987d58a9cbc d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in gid_table_release_one
2025/12/05 01:44 linux-next bc04acf4aeca d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in gid_table_release_one
2025/11/21 03:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 3812f8fa7c83 280ea308 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
2025/11/13 05:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 74c964729281 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 WARNING in gid_table_release_one
* Struck through repros no longer work on HEAD.