syzbot


kernel BUG in ext4_flex_group_add

Status: premoderation: reported syz repro on 2025/08/19 11:38
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+04caf179a50e725a8fb1@syzkaller.appspotmail.com
First crash: 6d00h, last: 5d17h
Bug presence (2)
Date Name Commit Repro Result
2025/08/22 lts (merge base) f2198ea7eb3e syz [report] kernel BUG in ext4_flex_group_add
2025/08/22 upstream (ToT) 471b25a2fcbb syz [report] kernel BUG in ext4_flex_group_add
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 kernel BUG in ext4_flex_group_add origin:upstream -1 C 2 8d18h 8d18h 0/2 upstream: reported C repro on 2025/08/16 17:59
android-5-10 kernel BUG in ext4_flex_group_add -1 syz 2 32d 122d 0/2 premoderation: reported syz repro on 2025/04/25 02:46

Sample crash report:
EXT4-fs (loop2): mounted filesystem without journal. Quota mode: writeback.
ext4 filesystem being mounted at /0/file0 supports timestamps until 2038-01-19 (0x7fffffff)
EXT4-fs (loop2): resizing filesystem from 0 to 8 blocks
------------[ cut here ]------------
kernel BUG at fs/ext4/resize.c:550!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 375 Comm: syz.2.17 Not tainted 6.1.145-syzkaller-00015-g87b9d836c3d8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:setup_new_flex_group_blocks fs/ext4/resize.c:549 [inline]
RIP: 0010:ext4_flex_group_add+0x4c2f/0x4c40 fs/ext4/resize.c:1559
Code: ff ff e8 34 75 7f ff 0f 0b e8 2d 75 7f ff 0f 0b e8 26 75 7f ff 0f 0b e8 1f 75 7f ff 0f 0b e8 18 75 7f ff 0f 0b e8 11 75 7f ff <0f> 0b e8 0a 75 7f ff 0f 0b 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc900009b7420 EFLAGS: 00010293
RAX: ffffffff81f0921f RBX: ffff88812a122400 RCX: ffff8881145a8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900009b76b0 R08: 0000000000000040 R09: 0000000000000003
R10: fffff52000136e5c R11: 1ffff92000136e5c R12: 1ffff110228b3700
R13: ffff888114963000 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f27ec77e6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27ec75cf98 CR3: 000000012d377000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_resize_fs+0x347d/0x4300 fs/ext4/resize.c:2174
 __ext4_ioctl fs/ext4/ioctl.c:1447 [inline]
 ext4_ioctl+0x2561/0x3b20 fs/ext4/ioctl.c:1614
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0x12f/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:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f27eb98ebe9
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:00007f27ec77e038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f27ebbb5fa0 RCX: 00007f27eb98ebe9
RDX: 0000200000000140 RSI: 0000000040086610 RDI: 0000000000000004
RBP: 00007f27eba11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f27ebbb6038 R14: 00007f27ebbb5fa0 R15: 00007ffea9e78618
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:setup_new_flex_group_blocks fs/ext4/resize.c:549 [inline]
RIP: 0010:ext4_flex_group_add+0x4c2f/0x4c40 fs/ext4/resize.c:1559
Code: ff ff e8 34 75 7f ff 0f 0b e8 2d 75 7f ff 0f 0b e8 26 75 7f ff 0f 0b e8 1f 75 7f ff 0f 0b e8 18 75 7f ff 0f 0b e8 11 75 7f ff <0f> 0b e8 0a 75 7f ff 0f 0b 0f 1f 84 00 00 00 00 00 90 90 90 90 90
RSP: 0018:ffffc900009b7420 EFLAGS: 00010293
RAX: ffffffff81f0921f RBX: ffff88812a122400 RCX: ffff8881145a8000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900009b76b0 R08: 0000000000000040 R09: 0000000000000003
R10: fffff52000136e5c R11: 1ffff92000136e5c R12: 1ffff110228b3700
R13: ffff888114963000 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f27ec77e6c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27ec75cf98 CR3: 000000012d377000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/19 18:51 android14-6.1 87b9d836c3d8 254a27c1 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-6-1 kernel BUG in ext4_flex_group_add
2025/08/19 11:37 android14-6.1 87b9d836c3d8 523f460e .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-6-1 kernel BUG in ext4_flex_group_add
* Struck through repros no longer work on HEAD.