linux-kernel - Re: [PATCH] ocfs2: Add i

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Message-ID: <606d781a-2d5c-48fc-bc67-4c7ff66a1dd7@linux.alibaba.com>
Date: Wed, 21 Aug 2024 18:41:06 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Edward Adam Davis <eadavis@...com>
Cc: jlbec@...lplan.org, linux-kernel@...r.kernel.org, mark@...heh.com,
 ocfs2-devel@...ts.linux.dev,
 syzbot+5a64828fcc4c2ad9b04f@...kaller.appspotmail.com,
 syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] ocfs2: Add i_size check for dir



On 8/20/24 9:55 PM, Edward Adam Davis wrote:
> On Tue, 20 Aug 2024 20:44:37 +0800, Joseph Qi wrote:
>>> When the i_size of dir is too large, it will cause limit to overflow and
>>> be less than de_buf, ultimately resulting in last_de not being initialized
>>> and causing uaf issue.
>>>
>>> Reported-and-tested-by: syzbot+5a64828fcc4c2ad9b04f@...kaller.appspotmail.com
>>> Signed-off-by: Edward Adam Davis <eadavis@...com>
>>> ---
>>>  fs/ocfs2/dir.c | 2 ++
>>>  1 file changed, 2 insertions(+)
>>>
>>> diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
>>> index d620d4c53c6f..c308dba6d213 100644
>>> --- a/fs/ocfs2/dir.c
>>> +++ b/fs/ocfs2/dir.c
>>> @@ -3343,6 +3343,8 @@ static int ocfs2_find_dir_space_id(struct inode *dir, struct buffer_head *di_bh,
>>>  	unsigned long offset = 0;
>>>  	unsigned int rec_len, new_rec_len, free_space;
>>>
>>> +	if (i_size_read(dir) > OCFS2_MAX_BLOCKSIZE)
>>> +		return -EINVAL;
>>
>> Why OCFS2_MAX_BLOCKSIZE?
> I think it is largest block size in ocfs2, therefore, if it is larger
> than it, it must be incorrect, even though the value of i_size in dir
> in the current issue is much larger than it (i_size_read(dir) is 0x900000000000100).
>> It seems that this is caused by a corrupted dir inode, since this is an
>> inline case, we may try best to make sure it won't exceeds block size?
>> i.e. dir->i_sb->s_blocksize.
> You mean dir->i_sb->s_blocksize bigger than OCFS2_MAX_BLOCKSIZE?
> 
No, I mean check s_blocksize seems more reasonable rather than
OCFS2_MAX_BLOCKSIZE.

Thanks,
Joseph