kernel BUG in ext4_ext_insert_index

Status: upstream: reported C repro on 2025/05/12 05:54
Reported-by: syzbot+fbce9d1fb2a8d5af8fa7@syzkaller.appspotmail.com
First crash: 512d, last: 92d
Fix bisection: fixed by (bisect log) :
commit 5ad6d994255e27a3254079dfb50ca861fc31f2d0
Author: Helen Koike <koike@igalia.com>
Date: Tue Mar 17 14:23:10 2026 +0000

  ext4: reject mount if bigalloc with s_first_data_block != 0

  
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 kernel BUG in ext4_ext_insert_index origin:lts -1 syz, C error 9 173d 342d 0/2 upstream: reported C repro on 2025/10/28 23:50
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/10/02 23:33 13m retest repro android13-5.10-lts no crash job log log
2026/10/02 23:33 12m retest repro android13-5.10-lts no crash job log log
2026/10/02 23:33 1h06m retest repro android13-5.10-lts no crash job log log
2026/09/07 06:07 19m retest repro android13-5.10-lts no crash job log log
2026/09/07 06:07 17m retest repro android13-5.10-lts no crash job log log
2026/09/07 06:07 18m retest repro android13-5.10-lts no crash job log log
2026/09/07 06:07 15m retest repro android13-5.10-lts no crash job log log
2026/08/20 09:53 22m retest repro android13-5.10-lts no crash job log log
2026/08/20 09:53 21m retest repro android13-5.10-lts no crash job log log
2026/08/20 09:53 22m retest repro android13-5.10-lts no crash job log log
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/08/06 14:13 7h58m bisect fix android13-5.10-lts OK (1) job log
2026/07/05 18:16 1h15m bisect fix android13-5.10-lts OK (0) job log log
2026/06/05 07:26 1h14m bisect fix android13-5.10-lts OK (0) job log log

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:1014!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 1784 Comm: syz.9.356 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:ext4_ext_insert_index+0x52d/0x530 fs/ext4/extents.c:1014
Code: 4c 89 fa e9 ca fd ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c dd fd ff ff 4c 89 f7 e8 ad e5 d2 ff e9 d0 fd ff ff e8 c3 65 98 ff <0f> 0b 90 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 81 ec c0 00 00
RSP: 0018:ffffc90000c16b20 EFLAGS: 00010287
RAX: ffffffff81cc4d8d RBX: ffff8881326f2418 RCX: 0000000000080000
RDX: ffffc90004547000 RSI: 00000000000083b3 RDI: 00000000000083b4
RBP: ffffc90000c16b90 R08: ffff88811a63e73f R09: 1ffff110234c7ce7
R10: dffffc0000000000 R11: ffffed10234c7ce8 R12: 0000000000000000
R13: 0000000000000192 R14: 00000000ffffffff R15: 0000000000000054
FS:  00007fa16dbd76c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555897d5908 CR3: 00000001225d3000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ext4_ext_split fs/ext4/extents.c:1272 [inline]
 ext4_ext_create_new_leaf fs/ext4/extents.c:1414 [inline]
 ext4_ext_insert_extent+0x3948/0x45d0 fs/ext4/extents.c:2098
 ext4_ext_map_blocks+0x17a9/0x5dd0 fs/ext4/extents.c:4362
 ext4_map_blocks+0x985/0x1bd0 fs/ext4/inode.c:674
 _ext4_get_block+0x1d1/0x4e0 fs/ext4/inode.c:817
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:848
 ext4_block_write_begin+0x573/0x1340 fs/ext4/inode.c:1101
 ext4_write_begin+0x67e/0x1690 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x478/0xf10 fs/ext4/inode.c:3033
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 ext4_buffered_write_iter+0x4b8/0x640 fs/ext4/file.c:271
 ext4_file_write_iter+0x53f/0x1980 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x758/0xdc0 fs/read_write.c:605
 ksys_pwrite64 fs/read_write.c:712 [inline]
 __do_sys_pwrite64 fs/read_write.c:722 [inline]
 __se_sys_pwrite64 fs/read_write.c:719 [inline]
 __x64_sys_pwrite64+0x197/0x220 fs/read_write.c:719
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7fa16f5e1799
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:00007fa16dbd7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007fa16f85b270 RCX: 00007fa16f5e1799
RDX: 00000000fffffd4a RSI: 0000200000000100 RDI: 000000000000000a
RBP: 00007fa16f677c99 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000004fed3 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa16f85b308 R14: 00007fa16f85b270 R15: 00007fffb7535f88
Modules linked in:
---[ end trace 8e93ae865c24a88b ]---
RIP: 0010:ext4_ext_insert_index+0x52d/0x530 fs/ext4/extents.c:1014
Code: 4c 89 fa e9 ca fd ff ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c dd fd ff ff 4c 89 f7 e8 ad e5 d2 ff e9 d0 fd ff ff e8 c3 65 98 ff <0f> 0b 90 55 48 89 e5 41 57 41 56 41 55 41 54 53 48 81 ec c0 00 00
RSP: 0018:ffffc90000c16b20 EFLAGS: 00010287
RAX: ffffffff81cc4d8d RBX: ffff8881326f2418 RCX: 0000000000080000
RDX: ffffc90004547000 RSI: 00000000000083b3 RDI: 00000000000083b4
RBP: ffffc90000c16b90 R08: ffff88811a63e73f R09: 1ffff110234c7ce7
R10: dffffc0000000000 R11: ffffed10234c7ce8 R12: 0000000000000000
R13: 0000000000000192 R14: 00000000ffffffff R15: 0000000000000054
FS:  00007fa16dbd76c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f341dd93000 CR3: 00000001225d3000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (20):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/25 05:27 android13-5.10-lts 9136079e403a 74e70d19 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2026/03/25 02:48 android13-5.10-lts 9136079e403a 74e70d19 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2026/03/24 06:38 android13-5.10-lts 9136079e403a baf8bf12 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2026/02/05 03:40 android13-5.10-lts 186f761c519d ea10c935 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/09/26 12:45 android13-5.10-lts 911f602c2237 0abd0691 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/07/11 09:51 android13-5.10-lts 59e9a7228857 3cda49cf .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/07/11 08:46 android13-5.10-lts 59e9a7228857 3cda49cf .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/07/11 06:50 android13-5.10-lts 59e9a7228857 3cda49cf .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/07/11 05:37 android13-5.10-lts 59e9a7228857 3cda49cf .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/06/17 07:53 android13-5.10-lts d76d4cd0623a cfebc887 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/06/17 06:33 android13-5.10-lts d76d4cd0623a cfebc887 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/06/16 19:21 android13-5.10-lts d76d4cd0623a d1716036 .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/06/01 07:39 android13-5.10-lts cf6ed0f1511d 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/31 04:44 android13-5.10-lts cf6ed0f1511d 3d2f584d .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/12 07:53 android13-5.10-lts 7e2543346ff7 77908e5f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/12 07:52 android13-5.10-lts 7e2543346ff7 77908e5f .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/12 07:09 android13-5.10-lts 7e2543346ff7 77908e5f .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/12 06:29 android13-5.10-lts 7e2543346ff7 77908e5f .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/12 05:47 android13-5.10-lts 7e2543346ff7 77908e5f .config strace log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
2025/05/12 05:02 android13-5.10-lts 7e2543346ff7 77908e5f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 kernel BUG in ext4_ext_insert_index
* Struck through repros no longer work on HEAD.