Re: [PATCH] xfs: fix null pointer dereference when mapping is NULL

[Eric Sandeen]

On 9/3/15 5:45 AM, Brian Foster wrote:
> On Thu, Sep 03, 2015 at 10:57:40AM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>
>> xfs_vm_set_page_dirty checks to see if mapping is NULL however
>> before this unlikely check it already dereferenced mapping when
>> initializing inode. Move the inode initialization after the mapping
>> null check to avoid a potential null pointer dereference.
>>
>> Fixes: 22e757a49cf0 ("xfs: don't dirty buffers beyond EOF")
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> ---
> 
> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>

Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>

Should probably cc: stable on this one too, the commit it
fixes went in at 3.17, and it also cc'd stable.

-Eric

>>  fs/xfs/xfs_aops.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
>> index c77499b..d15ae85 100644
>> --- a/fs/xfs/xfs_aops.c
>> +++ b/fs/xfs/xfs_aops.c
>> @@ -1935,7 +1935,7 @@ xfs_vm_set_page_dirty(
>>  	struct page		*page)
>>  {
>>  	struct address_space	*mapping = page->mapping;
>> -	struct inode		*inode = mapping->host;
>> +	struct inode		*inode;
>>  	loff_t			end_offset;
>>  	loff_t			offset;
>>  	int			newly_dirty;
>> @@ -1944,6 +1944,7 @@ xfs_vm_set_page_dirty(
>>  	if (unlikely(!mapping))
>>  		return !TestSetPageDirty(page);
>>  
>> +	inode = mapping->host;
>>  	end_offset = i_size_read(inode);
>>  	offset = page_offset(page);
>>  
>> -- 
>> 2.5.0
>>
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>> http://oss.sgi.com/mailman/listinfo/xfs
> 
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> http://oss.sgi.com/mailman/listinfo/xfs
> 

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