syzbot


kernel BUG in ext4_flex_group_add

Status: upstream: reported C repro on 2025/08/16 17:59
Reported-by: syzbot+fd854876b6f3b0d44019@syzkaller.appspotmail.com
First crash: 7d08h, last: 7d06h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 kernel BUG in ext4_flex_group_add origin:upstream -1 syz 2 4d05h 4d13h 0/2 premoderation: reported syz repro on 2025/08/19 11:38
android-5-10 kernel BUG in ext4_flex_group_add -1 syz 2 31d 120d 0/2 premoderation: reported syz repro on 2025/04/25 02:46

Sample crash report:
loop2: detected capacity change from 0 to 512
EXT4-fs (loop2): mounted filesystem without journal. Opts: ,errors=continue. 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:546!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 373 Comm: syz.2.17 Not tainted 5.15.189-syzkaller-android13-5.15.189_r00 #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:545 [inline]
RIP: 0010:ext4_flex_group_add+0x5395/0x53a0 fs/ext4/resize.c:1512
Code: ff ff e8 2e 6c 88 ff 0f 0b e8 27 6c 88 ff 0f 0b e8 20 6c 88 ff 0f 0b e8 19 6c 88 ff 0f 0b e8 12 6c 88 ff 0f 0b e8 0b 6c 88 ff <0f> 0b e8 04 6c 88 ff 0f 0b 66 90 55 48 89 e5 41 57 41 56 41 55 41
RSP: 0018:ffffc900040ef4c0 EFLAGS: 00010293
RAX: ffffffff81e043c5 RBX: ffff88812c3f2400 RCX: ffff888110052780
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900040ef7b0 R08: 0000000000000004 R09: 0000000000000003
R10: fffff5200081de84 R11: 1ffff9200081de84 R12: 1ffff11022109000
R13: ffff888110c9b000 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f413696a6c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4136949d58 CR3: 000000012e2a7000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ext4_resize_fs+0x39aa/0x4370 fs/ext4/resize.c:2127
 __ext4_ioctl fs/ext4/ioctl.c:1079 [inline]
 ext4_ioctl+0x2164/0x33c0 fs/ext4/ioctl.c:1282
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0x121/0x1a0 fs/ioctl.c:860
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:860
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f4136af9be9
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:00007f413696a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4136d20fa0 RCX: 00007f4136af9be9
RDX: 0000200000000140 RSI: 0000000040086610 RDI: 0000000000000004
RBP: 00007f4136b7ce19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4136d21038 R14: 00007f4136d20fa0 R15: 00007fffb9a4f198
 </TASK>
Modules linked in:
---[ end trace 41d440f79df6b11e ]---
RIP: 0010:setup_new_flex_group_blocks fs/ext4/resize.c:545 [inline]
RIP: 0010:ext4_flex_group_add+0x5395/0x53a0 fs/ext4/resize.c:1512
Code: ff ff e8 2e 6c 88 ff 0f 0b e8 27 6c 88 ff 0f 0b e8 20 6c 88 ff 0f 0b e8 19 6c 88 ff 0f 0b e8 12 6c 88 ff 0f 0b e8 0b 6c 88 ff <0f> 0b e8 04 6c 88 ff 0f 0b 66 90 55 48 89 e5 41 57 41 56 41 55 41
RSP: 0018:ffffc900040ef4c0 EFLAGS: 00010293
RAX: ffffffff81e043c5 RBX: ffff88812c3f2400 RCX: ffff888110052780
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc900040ef7b0 R08: 0000000000000004 R09: 0000000000000003
R10: fffff5200081de84 R11: 1ffff9200081de84 R12: 1ffff11022109000
R13: ffff888110c9b000 R14: 0000000000000000 R15: 0000000000000001
FS:  00007f413696a6c0(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4136949d58 CR3: 000000012e2a7000 CR4: 00000000003506b0
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
2025/08/16 17:51 android13-5.15-lts f32b52534f1d 1804e95e .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 kernel BUG in ext4_flex_group_add
2025/08/16 16:34 android13-5.15-lts f32b52534f1d 1804e95e .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 kernel BUG in ext4_flex_group_add
* Struck through repros no longer work on HEAD.