Re: [PATCH] crypto: hash - Fix handling of small unaligned buffers

[David Miller <davem@xxxxxxxxxxxxx>]

From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 4 Aug 2010 21:48:51 +0800

> On Mon, Aug 02, 2010 at 02:45:37PM +0200, Szilveszter Ördög wrote:
>> If a scatterwalk chain contains an entry with an unaligned offset then
>> hash_walk_next() will cut off the next step at the next alignment point.
>> 
>> However, if the entry ends before the next alignment point then we will want to
>> process more data than it is available.
>> 
>> Fix this by checking whether the next aligment point is before the end of the
>> current entry.
>> ---
>>  crypto/ahash.c |    7 +++++--
>>  1 files changed, 5 insertions(+), 2 deletions(-)
>> 
>> diff --git a/crypto/ahash.c b/crypto/ahash.c
>> index b8c59b8..f669822 100644
>> --- a/crypto/ahash.c
>> +++ b/crypto/ahash.c
>> @@ -47,8 +47,11 @@ static int hash_walk_next(struct crypto_hash_walk *walk)
>>  	walk->data = crypto_kmap(walk->pg, 0);
>>  	walk->data += offset;
>> 
>> -	if (offset & alignmask)
>> -		nbytes = alignmask + 1 - (offset & alignmask);
>> +	if (offset & alignmask) {
>> +		unsigned int unaligned = alignmask + 1 - (offset & alignmask);
>> +		if (nbytes > unaligned)
>> +			nbytes = unaligned;
>> +	}
>> 
>>  	walk->entrylen -= nbytes;
>>  	return nbytes;
> 
> The patch looks OK to me.  Dave, what do you think?

Looks good, thanks Szilveszter:

Acked-by: David S. Miller <davem@xxxxxxxxxxxxx>
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