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kernel BUG in ext4_alloc_file_blocks

Status: upstream: reported C repro on 2025/10/10 15:21
Bug presence: origin:lts
[Documentation on labels]
Reported-by: syzbot+8c381bcee2948a154ec6@syzkaller.appspotmail.com
First crash: 245d, last: 12d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/10/12 lts (merge base) f97f1002271b C [report] kernel BUG in ext4_alloc_file_blocks
2025/10/12 upstream (ToT) 67029a49db6c C Didn't crash
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream kernel BUG in ext4_alloc_file_blocks ext4 -1 C error error 3 314d 442d 0/29 auto-obsoleted due to no activity on 2026/01/28 09:24
android-5-15 kernel BUG in ext4_alloc_file_blocks origin:upstream -1 C 2 30d 30d 0/2 upstream: reported C repro on 2026/05/13 12:45
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/04/07 20:48 7m retest repro android14-6.1 report log
2025/10/25 22:44 8m retest repro android14-6.1 report log
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/01/27 20:00 2m bisect fix android14-6.1 error job log
2025/12/28 17:59 2h01m bisect fix android14-6.1 OK (0) job log log
2025/11/25 17:51 2h09m bisect fix android14-6.1 OK (0) job log log

Sample crash report:
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:4497!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 1222 Comm: syz.6.220 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
RIP: 0010:ext4_alloc_file_blocks+0xb4f/0xb60 fs/ext4/extents.c:4497
Code: 8b 4c 24 10 80 e1 07 fe c1 38 c1 0f 8c 78 f6 ff ff 48 8b 7c 24 10 e8 b0 28 d0 ff e9 69 f6 ff ff e8 d6 b9 14 03 e8 d1 83 8a ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
RSP: 0018:ffffc90002857720 EFLAGS: 00010293
RAX: ffffffff81e6f7af RBX: 0000000000000003 RCX: ffff88811d64a880
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002857888 R08: ffff888132d4618f R09: 1ffff110265a8c31
R10: dffffc0000000000 R11: ffffed10265a8c32 R12: ffff888132d46188
R13: ffff888132d462a0 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fd9d08736c0(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff745d3ff0 CR3: 0000000114339000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_zero_range+0x449/0xd00 fs/ext4/extents.c:4647
 ext4_fallocate+0x562/0x1dc0 fs/ext4/extents.c:4782
 vfs_fallocate+0x4c5/0x5a0 fs/open.c:324
 ioctl_preallocate fs/ioctl.c:290 [inline]
 file_ioctl fs/ioctl.c:335 [inline]
 do_vfs_ioctl+0x1ad8/0x1cd0 fs/ioctl.c:849
 __do_sys_ioctl fs/ioctl.c:868 [inline]
 __se_sys_ioctl+0x9f/0x1b0 fs/ioctl.c:856
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
 x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 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: 0033:0x7fd9cf99ce59
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:00007fd9d0873028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd9cfc16090 RCX: 00007fd9cf99ce59
RDX: 0000200000000180 RSI: 0000000040305839 RDI: 0000000000000005
RBP: 00007fd9cfa32d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd9cfc16128 R14: 00007fd9cfc16090 R15: 00007fff241aa778
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:ext4_alloc_file_blocks+0xb4f/0xb60 fs/ext4/extents.c:4497
Code: 8b 4c 24 10 80 e1 07 fe c1 38 c1 0f 8c 78 f6 ff ff 48 8b 7c 24 10 e8 b0 28 d0 ff e9 69 f6 ff ff e8 d6 b9 14 03 e8 d1 83 8a ff <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41
RSP: 0018:ffffc90002857720 EFLAGS: 00010293
RAX: ffffffff81e6f7af RBX: 0000000000000003 RCX: ffff88811d64a880
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90002857888 R08: ffff888132d4618f R09: 1ffff110265a8c31
R10: dffffc0000000000 R11: ffffed10265a8c32 R12: ffff888132d46188
R13: ffff888132d462a0 R14: 0000000000000000 R15: 0000000000000000
FS:  00007fd9d08736c0(0000) GS:ffff8881f6e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff0043ea540 CR3: 0000000114339000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/31 17:50 android14-6.1 b28955bde980 6b4a8443 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 kernel BUG in ext4_alloc_file_blocks
2026/05/31 17:07 android14-6.1 b28955bde980 6b4a8443 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 kernel BUG in ext4_alloc_file_blocks
2025/10/10 15:20 android14-6.1 1257aa4519ee ff1712fe .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 kernel BUG in ext4_alloc_file_blocks
* Struck through repros no longer work on HEAD.