Re: [PATCH] xfsprogs: fix Out-of-bounds access in repair/dinode.c

[Eric Sandeen <sandeen@sandeen.net>]

On 8/23/13 11:38 AM, Ben Myers wrote:
> Hey Rich and Li Zhong,
> 
> On Wed, Aug 21, 2013 at 11:51:11AM -0500, Rich Johnston wrote:
>> Looks good, thanks for the patch Li Zhong. it has been committed.
>>
>> --Rich
>>
>> Reviewed-by: Rich Johnston <rjohnston@sgi.com>
>>
>> commit e7c05095f5baa9cd2e35a6de03d7dd9f51dd3910
>> Author: Li Zhong <zhong@linux.vnet.ibm.com>
>> Date:   Mon Aug 12 06:11:01 2013 +0000
>>
>>     xfsprogs: fix Out-of-bounds access in repair/dinode.c
>>
>> On 08/12/2013 01:11 AM, Li Zhong wrote:
>>> Following is reported by coverity in bug 1061528:
>>>
>>> 187                        __dirty_no_modify_ret(dirty);
>>>
>>> CID 1061528 (#1 of 1): Out-of-bounds access (OVERRUN)53. overrun-buffer-arg: Overrunning array "dinoc->di_pad" of 6 bytes by passing it to a function which accesses it at byte offset 15 using argument "16UL".
>>> 188                        memset(dinoc->di_pad, 0, 16);
>>>
>>> It seems that di_pad here should be di_pad2, as sekharan pointed out.
>>>
>>> Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
>>> ---
>>>  repair/dinode.c | 4 ++--
>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/repair/dinode.c b/repair/dinode.c
>>> index e607f0b..94bf2f8 100644
>>> --- a/repair/dinode.c
>>> +++ b/repair/dinode.c
>>> @@ -183,9 +183,9 @@ clear_dinode_core(struct xfs_mount *mp, xfs_dinode_t *dinoc, xfs_ino_t ino_num)
>>>  	}
>>>
>>>  	for (i = 0; i < 16; i++) {
>>> -		if (dinoc->di_pad[i] != 0) {
>>> +		if (dinoc->di_pad2[i] != 0) {
>>>  			__dirty_no_modify_ret(dirty);
>>> -			memset(dinoc->di_pad, 0, 16);
>>> +			memset(dinoc->di_pad2, 0, 16);
>>>  			break;
>>>  		}
>>>  	}
> 
> We also discussed this issue a bit in this thread:
> http://oss.sgi.com/archives/xfs/2013-08/msg00228.html
> 
> Looks like the loop itself is incorrect and should be removed, and Eric has
> suggested that the conditional be changed to a memcmp in case the size of the
> pad changes in the future.  Would either of you care to spin up another patch
> to clean it up?

I think I was confused; it seems fine as it is in git, not sure what I was
thinking.

memcmp can't use a bare "0" as an arg, so it's not ideal to use either.

Not a huge fan of the hard-coded 16, but I think the code is correct now; we
can probably move on to real problems.  ;)

-Eric

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