linux-kernel - Re: [PATCH V3 2/2] ocfs2: Fix uaf in ocfs2_set_buffer

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Message-ID: <7d0d7bbc-6265-4f60-ba2c-a9c15771e95e@suse.com>
Date: Wed, 21 Aug 2024 10:39:39 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: Joseph Qi <joseph.qi@...ux.alibaba.com>, Lizhi Xu <lizhi.xu@...driver.com>
Cc: jlbec@...lplan.org, linux-kernel@...r.kernel.org, mark@...heh.com,
 ocfs2-devel@...ts.linux.dev,
 syzbot+ab134185af9ef88dfed5@...kaller.appspotmail.com,
 syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V3 2/2] ocfs2: Fix uaf in ocfs2_set_buffer_uptodate

On 8/21/24 10:34, Joseph Qi wrote:
> And this is not a UAF case, but NULL pointer dereference.
> So I suggest change the subject to:
> ocfs2: fix possible NULL pointer dereference in ocfs2_set_buffer_uptodate

I agree with above too.
I didn't care about the patch subject in previous review jobs, 'UAF' is not suitable.

-Heming

> 
> On 8/21/24 8:08 AM, Joseph Qi wrote:
>>
>>
>> On 8/20/24 5:45 PM, Lizhi Xu wrote:
>>> In the for-loop after the 'read_failure' label, the condition
>>> '(bh == NULL) && flags includes OCFS2_BH_READAHEAD' is missing.
>>> When this contidion is true, this for-loop will call ocfs2_set_buffer
>>> _uptodate(ci, bh), which then triggers a NULL pointer access error.
>>>
>>
>> Or it may simplified as the following:
>>
>> When doing cleanup, if flags without OCFS2_BH_READAHEAD, it may trigger
>> NULL pointer dereference in the following ocfs2_set_buffer_uptodate() if
>> bh is NULL.
>>
>>> Changes from V2:
>>> * Make the code more concise
>>>
>>
>> This is not the right place for changelog.
>>
>> Thanks,
>> Joseph
>>
>>> Reported-and-suggested-by: Heming Zhao <heming.zhao@...e.com>
>>> Signed-off-by: Lizhi Xu <lizhi.xu@...driver.com>
>>> Reviewed-by: Heming Zhao <heming.zhao@...e.com>
>>> ---
>>>   fs/ocfs2/buffer_head_io.c | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/ocfs2/buffer_head_io.c b/fs/ocfs2/buffer_head_io.c
>>> index e62c7e1de4eb..8f714406528d 100644
>>> --- a/fs/ocfs2/buffer_head_io.c
>>> +++ b/fs/ocfs2/buffer_head_io.c
>>> @@ -388,7 +388,8 @@ int ocfs2_read_blocks(struct ocfs2_caching_info *ci, u64 block, int nr,
>>>   		/* Always set the buffer in the cache, even if it was
>>>   		 * a forced read, or read-ahead which hasn't yet
>>>   		 * completed. */
>>> -		ocfs2_set_buffer_uptodate(ci, bh);
>>> +		if (bh)
>>> +			ocfs2_set_buffer_uptodate(ci, bh);
>>>   	}
>>>   	ocfs2_metadata_cache_io_unlock(ci);
>>>