syzbot


kernel BUG in may_open (2)

Status: upstream: reported C repro on 2025/07/08 17:51
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+895c23f6917da440ed0d@syzkaller.appspotmail.com
Fix commit: cramfs: Verify inode mode when loading from disk isofs: Verify inode mode when loading from disk jfs: Verify inode mode when loading from disk minixfs: Verify inode mode when loading from disk nilfs2: reject invalid file types when reading inodes ntfs3: pretend $Extend records as regular files squashfs: verify inode mode when loading from disk
Patched on: [ci-upstream-gce-arm64 ci-upstream-kasan-badwrites-root ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-smack-root ci-upstream-kmsan-gce-386-root ci-upstream-kmsan-gce-root], missing on: [ci-qemu-gce-upstream-auto ci-qemu-native-arm64-kvm ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-qemu2-riscv64 ci-snapshot-upstream-root ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-leak ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci-upstream-rust-kasan-gce ci2-upstream-fs ci2-upstream-kcsan-gce ci2-upstream-usb]
First crash: 132d, last: 15m
Cause bisection: introduced by (bisect log) :
commit af153bb63a336a7ca0d9c8ef4ca98119c5020030
Author: Mateusz Guzik <mjguzik@gmail.com>
Date: Sun Feb 9 18:55:21 2025 +0000

  vfs: catch invalid modes in may_open()

Crash: kernel BUG in may_open (log)
Repro: C syz .config
  
Discussions (16)
Title Replies (including bot) Last reply
[PATCH v2] hfsplus: Verify inode mode when loading from disk 1 (1) 2025/11/15 09:18
[PATCH v2 (REPOST)] bfs: Reconstruct file type when loading from disk 1 (1) 2025/10/23 13:25
[PATCH v2] bfs: Reconstruct file type when loading from disk 1 (1) 2025/10/13 05:44
[PATCH] bfs: Verify inode mode when loading from disk 1 (1) 2025/10/10 14:24
[PATCH] hfsplus: Verify inode mode when loading from disk 2 (2) 2025/10/07 14:22
[PATCH] jfs: Verify inode mode when loading from disk 5 (5) 2025/09/17 18:21
[PATCH] ntfs3: pretend $Extend records as regular files 1 (1) 2025/09/02 10:43
[PATCH] cramfs: Verify inode mode when loading from disk 4 (4) 2025/08/30 10:01
[PATCH] squashfs: Verify inode mode when loading from disk 2 (2) 2025/08/14 15:14
Re: [PATCH] vfs: show filesystem name at dump_inode() 1 (1) 2025/08/12 15:22
[PATCH] minixfs: Verify inode mode when loading from disk 1 (1) 2025/08/12 15:17
[PATCH] vfs: show filesystem name at dump_inode() 2 (2) 2025/08/11 19:45
[RFC PATCH] vfs: exclude ntfs3 from file mode validation in may_open() 3 (3) 2025/08/11 13:50
[PATCH] isofs: Verify inode mode when loading from disk 4 (4) 2025/07/11 09:39
[PATCH] nilfs2: reject invalid file types when reading inodes 1 (1) 2025/07/10 13:49
[syzbot] [nilfs?] kernel BUG in may_open (2) 3 (4) 2025/07/10 07:42
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream kernel BUG in may_open fs -1 C error 137019 132d 228d 29/29 fixed on 2025/07/08 00:33

Sample crash report:
loop0: detected capacity change from 0 to 4096
ntfs3(loop0): Different NTFS sector size (4096) and media sector size (512).
VFS_BUG_ON_INODE(!IS_ANON_FILE(inode)) encountered for inode ffff8880493dd770
------------[ cut here ]------------
kernel BUG at fs/namei.c:3474!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 6034 Comm: syz.0.17 Tainted: G        W           syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:may_open+0x4b1/0x4c0 fs/namei.c:3474
Code: 38 c1 0f 8c 1e fd ff ff 4c 89 e7 e8 79 69 f0 ff e9 11 fd ff ff e8 7f 36 91 ff 4c 89 f7 48 c7 c6 80 cf 18 8b e8 c0 bb fa fe 90 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90
RSP: 0018:ffffc900048e78e0 EFLAGS: 00010246
RAX: 000000000000004d RBX: dffffc0000000000 RCX: 7e27dcd5c4ee3100
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000008042 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff5200091cec1 R12: 0000000000000000
R13: ffffffff8daf9340 R14: ffff8880493dd770 R15: 0000000000000006
FS:  000055558fb23500(0000) GS:ffff8881269c5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdb4d546000 CR3: 0000000042b20000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 do_open fs/namei.c:3885 [inline]
 path_openat+0x2d9d/0x3840 fs/namei.c:4046
 do_filp_open+0x1fa/0x410 fs/namei.c:4073
 do_sys_openat2+0x121/0x1c0 fs/open.c:1435
 do_sys_open fs/open.c:1450 [inline]
 __do_sys_openat fs/open.c:1466 [inline]
 __se_sys_openat fs/open.c:1461 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1461
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdb552debe9
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:00007ffc47064168 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fdb55505fa0 RCX: 00007fdb552debe9
RDX: 0000000000000042 RSI: 0000200000000080 RDI: ffffffffffffff9c
RBP: 00007fdb55361e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdb55505fa0 R14: 00007fdb55505fa0 R15: 0000000000000004
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:may_open+0x4b1/0x4c0 fs/namei.c:3474
Code: 38 c1 0f 8c 1e fd ff ff 4c 89 e7 e8 79 69 f0 ff e9 11 fd ff ff e8 7f 36 91 ff 4c 89 f7 48 c7 c6 80 cf 18 8b e8 c0 bb fa fe 90 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90
RSP: 0018:ffffc900048e78e0 EFLAGS: 00010246
RAX: 000000000000004d RBX: dffffc0000000000 RCX: 7e27dcd5c4ee3100
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000008042 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff5200091cec1 R12: 0000000000000000
R13: ffffffff8daf9340 R14: ffff8880493dd770 R15: 0000000000000006
FS:  000055558fb23500(0000) GS:ffff8881269c5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fdb4d546000 CR3: 0000000042b20000 CR4: 00000000003526f0

Crashes (17459):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/22 02:11 upstream 068a56e56fa8 3e79b825 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/08/21 23:21 upstream 068a56e56fa8 3e79b825 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/08/21 17:40 upstream 068a56e56fa8 3e79b825 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/08/19 12:36 upstream be48bcf004f9 523f460e .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] [mounted in repro #3 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/07/08 13:03 upstream d7b8f8e20813 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs kernel BUG in may_open
2025/07/08 12:34 upstream d7b8f8e20813 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs kernel BUG in may_open
2025/07/08 12:04 upstream d7b8f8e20813 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs kernel BUG in may_open
2025/07/08 04:06 upstream d7b8f8e20813 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs kernel BUG in may_open
2025/07/08 02:39 upstream d7b8f8e20813 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-upstream-fs kernel BUG in may_open
2025/07/08 01:41 upstream d7b8f8e20813 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs kernel BUG in may_open
2025/07/22 16:08 upstream 89be9a83ccf1 af30dea9 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root kernel BUG in may_open
2025/07/22 09:21 upstream 89be9a83ccf1 1555463b .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root kernel BUG in may_open
2025/07/19 03:20 upstream d786aba32000 7117feec .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root kernel BUG in may_open
2025/07/08 01:56 upstream d7b8f8e20813 4f67c4ae .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root kernel BUG in may_open
2025/07/08 01:21 upstream d7b8f8e20813 4f67c4ae .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro] ci-snapshot-upstream-root kernel BUG in may_open
2025/07/12 16:37 linux-next a62b7a37e6fc 3cda49cf .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-linux-next-kasan-gce-root kernel BUG in may_open
2025/07/08 01:57 linux-next 26ffb3d6f02c 4f67c4ae .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root kernel BUG in may_open
2025/07/08 02:15 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7482bb149b9f 4f67c4ae .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-gce-arm64 kernel BUG in may_open
2025/07/08 01:34 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci 7482bb149b9f 4f67c4ae .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-gce-arm64 kernel BUG in may_open
2025/08/19 10:11 upstream be48bcf004f9 523f460e .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] [mounted in repro #3 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/08/19 08:10 upstream be48bcf004f9 523f460e .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] [mounted in repro #3 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/08/19 06:10 upstream be48bcf004f9 523f460e .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2 (clean fs)] [mounted in repro #3 (clean fs)] ci2-upstream-fs kernel BUG in may_open
2025/11/17 10:24 upstream 6a23ae0a96a6 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/17 05:46 upstream 7254a2b52279 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root kernel BUG in may_open
2025/11/17 01:32 upstream 7254a2b52279 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/16 12:19 upstream f824272b6e3f f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/16 10:03 upstream f824272b6e3f f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/16 08:12 upstream f824272b6e3f f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/16 05:46 upstream f824272b6e3f f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/16 02:38 upstream f824272b6e3f f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 23:06 upstream f824272b6e3f f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 19:38 upstream 7a0892d2836e f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 16:22 upstream 7a0892d2836e f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 12:59 upstream 7a0892d2836e f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 06:44 upstream d4f8cccc6230 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 05:11 upstream d4f8cccc6230 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 03:37 upstream d4f8cccc6230 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/15 01:03 upstream 6da43bbeb691 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root kernel BUG in may_open
2025/11/14 23:11 upstream d4f8cccc6230 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/14 17:54 upstream 6da43bbeb691 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/14 16:29 upstream 6da43bbeb691 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/14 09:37 upstream 6da43bbeb691 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/14 08:17 upstream 6da43bbeb691 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/14 04:17 upstream 2ccec5944606 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/14 00:37 upstream 2ccec5944606 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/13 15:13 upstream e927c520e1ba 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/13 13:24 upstream e927c520e1ba 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/13 10:30 upstream e927c520e1ba 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/13 06:39 upstream e927c520e1ba 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/13 02:07 upstream 24172e0d7990 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/13 00:12 upstream 24172e0d7990 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/12 22:55 upstream 24172e0d7990 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/12 20:37 upstream 24172e0d7990 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/12 18:19 upstream 24172e0d7990 07e030de .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/12 10:14 upstream 24172e0d7990 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/12 08:20 upstream 24172e0d7990 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/11/12 00:05 upstream 24172e0d7990 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs kernel BUG in may_open
2025/10/08 11:39 upstream 971199ad2a0f 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-badwrites-root kernel BUG in may_open
2025/11/16 21:29 upstream 7254a2b52279 f7988ea4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/16 20:17 upstream 7254a2b52279 f7988ea4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/16 18:27 upstream 7254a2b52279 f7988ea4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/16 01:02 upstream f824272b6e3f f7988ea4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/14 21:13 upstream 6da43bbeb691 6d98c1c8 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/14 19:34 upstream 6da43bbeb691 6d98c1c8 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/14 06:47 upstream 2ccec5944606 07e030de .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/13 23:57 upstream 2ccec5944606 07e030de .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/13 19:00 upstream 2ccec5944606 07e030de .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/13 09:02 upstream e927c520e1ba 07e030de .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/12 16:28 upstream 24172e0d7990 07e030de .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/11/12 07:16 upstream 24172e0d7990 4e1406b4 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root kernel BUG in may_open
2025/10/26 09:09 linux-next 72fb0170ef1f c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root kernel BUG in may_open
2025/11/17 07:59 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci db9030a787e3 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 kernel BUG in may_open
2025/11/17 03:30 git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci db9030a787e3 f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-gce-arm64 kernel BUG in may_open
2025/11/13 01:01 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 kernel BUG in may_open
* Struck through repros no longer work on HEAD.