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

[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 <gaoxiang25@xxxxxxxxxx>
> 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
needed.)

Thanks,
Gao Xiang

> 
> 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+8afc256dce324523609d@xxxxxxxxxxxxxxxxxxxxxxxxx
> 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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> 
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> syzbot can test patches for this issue, for details see:
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