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

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Message-ID: <416247e6-5da7-401c-815f-a4cf8ae37d51@linux.alibaba.com>
Date: Wed, 21 Aug 2024 10:34:48 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Lizhi Xu <lizhi.xu@...driver.com>, heming.zhao@...e.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

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

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);
>>