kernel BUG at fs/erofs/inode.c:LINE!

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d1d2220c Add linux-next specific files for 20200924
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=166cb7d9900000
kernel config: https://syzkaller.appspot.com/x/.config?x=254e028a642027c
dashboard link: https://syzkaller.appspot.com/bug?extid=8afc256dce324523609d
compiler: gcc (GCC) 10.1.0-syz 20200507
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127762c3900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=124ccf3b900000

The issue was bisected to:

commit 382329a9d8553a98418a6f6e3425f0c288837897
Author: Gao Xiang <gaoxi...@huawei.com>
Date: Wed Aug 14 10:37:04 2019 +0000

staging: erofs: differentiate unsupported on-disk format

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=149889e3900000
final oops: https://syzkaller.appspot.com/x/report.txt?x=169889e3900000
console output: https://syzkaller.appspot.com/x/log.txt?x=129889e3900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8afc25...@syzkaller.appspotmail.com
Fixes: 382329a9d855 ("staging: erofs: differentiate unsupported on-disk format")

erofs: (device loop0): erofs_read_inode: bogus i_mode (0) @ nid 36
------------[ cut here ]------------
kernel BUG at fs/erofs/inode.c:182!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 6895 Comm: syz-executor894 Not tainted 5.9.0-rc6-next-20200924-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:erofs_read_inode fs/erofs/inode.c:182 [inline]
RIP: 0010:erofs_fill_inode fs/erofs/inode.c:235 [inline]
RIP: 0010:erofs_iget+0xfd8/0x2390 fs/erofs/inode.c:322
Code: 00 0f 85 aa 10 00 00 49 8b 7c 24 28 49 89 d8 44 89 e9 48 c7 c2 a0 9c ef 88 48 c7 c6 40 9f ef 88 e8 b5 df b0 04 e8 88 5a 07 fe <0f> 0b e8 81 5a 07 fe 4c 89 e7 4c 63 e3 e8 b6 61 5b fe e9 ed f0 ff
RSP: 0018:ffffc90001017c10 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000024 RCX: 0000000000000000
RDX: ffff8880a172e480 RSI: ffffffff836dd6e8 RDI: fffff52000202f72
RBP: ffff8880a8ca4480 R08: 0000000000000042 R09: ffff8880ae5319a7
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880854fd9b8
R13: 0000000000000000 R14: ffffea0002a32900 R15: 0000000000000000
FS: 000000000108e880(0000) GS:ffff8880ae500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043eb80 CR3: 00000000a7edb000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
erofs_fc_fill_super+0xaa3/0x1010 fs/erofs/super.c:382
get_tree_bdev+0x421/0x740 fs/super.c:1342
vfs_get_tree+0x89/0x2f0 fs/super.c:1547
do_new_mount fs/namespace.c:2896 [inline]
path_mount+0x12ae/0x1e70 fs/namespace.c:3227
__do_sys_mount fs/namespace.c:3438 [inline]
__se_sys_mount fs/namespace.c:3411 [inline]
__x64_sys_mount+0x278/0x2f0 fs/namespace.c:3411
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x446d6a
Code: b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 fd ad fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 da ad fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:00007fffa8ef9ef8 EFLAGS: 00000297 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fffa8ef9f50 RCX: 0000000000446d6a
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007fffa8ef9f10
RBP: 00007fffa8ef9f10 R08: 00007fffa8ef9f50 R09: 00007fff00000015
R10: 0000000000000000 R11: 0000000000000297 R12: 0000000000000001
R13: 0000000000000004 R14: 0000000000000003 R15: 0000000000000003
Modules linked in:
---[ end trace 66a5371a9bd8a3b2 ]---
RIP: 0010:erofs_read_inode fs/erofs/inode.c:182 [inline]
RIP: 0010:erofs_fill_inode fs/erofs/inode.c:235 [inline]
RIP: 0010:erofs_iget+0xfd8/0x2390 fs/erofs/inode.c:322
Code: 00 0f 85 aa 10 00 00 49 8b 7c 24 28 49 89 d8 44 89 e9 48 c7 c2 a0 9c ef 88 48 c7 c6 40 9f ef 88 e8 b5 df b0 04 e8 88 5a 07 fe <0f> 0b e8 81 5a 07 fe 4c 89 e7 4c 63 e3 e8 b6 61 5b fe e9 ed f0 ff
RSP: 0018:ffffc90001017c10 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000024 RCX: 0000000000000000
RDX: ffff8880a172e480 RSI: ffffffff836dd6e8 RDI: fffff52000202f72
RBP: ffff8880a8ca4480 R08: 0000000000000042 R09: ffff8880ae5319a7
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880854fd9b8
R13: 0000000000000000 R14: ffffea0002a32900 R15: 0000000000000000
FS: 000000000108e880(0000) GS:ffff8880ae500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000043eb80 CR3: 00000000a7edb000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Gao Xiang]

Hi,

On Mon, Sep 28, 2020 at 12:27:24AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: d1d2220c Add linux-next specific files for 20200924
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=166cb7d9900000
> kernel config: https://syzkaller.appspot.com/x/.config?x=254e028a642027c
> dashboard link: https://syzkaller.appspot.com/bug?extid=8afc256dce324523609d
> compiler: gcc (GCC) 10.1.0-syz 20200507
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127762c3900000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=124ccf3b900000
>
> The issue was bisected to:
>
> commit 382329a9d8553a98418a6f6e3425f0c288837897
> Author: Gao Xiang <gaoxi...@huawei.com>
> Date: Wed Aug 14 10:37:04 2019 +0000
>
> staging: erofs: differentiate unsupported on-disk format

if CONFIG_EROFS_DEBUG = y, the kernel will also BUG_ON on
currupted images in order to check potential mkfs fault.

So it's an expected behavior for now (if syzbot needs more
requirement, e.g. differ from runtime error vs corrupted error,
I can do it if needed.)

Thanks,
Gao Xiang

[Chao Yu]

Hi syzbot administrator,

CONFIG_EROFS_DEBUG was introduced for debug purpose during
development, this should not be enabled on release version.

Can you please turn off this config, and retest with erofs module?

Thanks,

On 2020/9/29 4:36, Gao Xiang wrote:
> Hi,
>
> On Mon, Sep 28, 2020 at 12:27:24AM -0700, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: d1d2220c Add linux-next specific files for 20200924
>> git tree: linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=166cb7d9900000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=254e028a642027c
>> dashboard link: https://syzkaller.appspot.com/bug?extid=8afc256dce324523609d
>> compiler: gcc (GCC) 10.1.0-syz 20200507
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127762c3900000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=124ccf3b900000
>>
>> The issue was bisected to:
>>
>> commit 382329a9d8553a98418a6f6e3425f0c288837897
>> Author: Gao Xiang <gaoxi...@huawei.com>
>> Date: Wed Aug 14 10:37:04 2019 +0000
>>
>> staging: erofs: differentiate unsupported on-disk format
>

> if CONFIG_EROFS_DEBUG=y, the kernel will also BUG_ON on

> currupted images in order to check potential mkfs fault.
>

> So it's an expected behavior for now (if syzbot needs some more requirement,
> e.g. differ from runtime error vs corrupted image error, I can do it if

> .
>

[Dmitry Vyukov]

On Tue, Sep 29, 2020 at 3:57 AM Chao Yu <yuc...@huawei.com> wrote:
>
> Hi syzbot administrator,
>
> CONFIG_EROFS_DEBUG was introduced for debug purpose during
> development, this should not be enabled on release version.
>
> Can you please turn off this config, and retest with erofs module?
>
> Thanks,

Hi Chao,

Thanks for looking into this. I've disabled CONFIG_EROFS_FS_DEBUG in
syzbot config:
https://github.com/google/syzkaller/commit/5abc3f1ab298244473b613c289f1536e366fcf04

#syz invalid

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