Re: [PATCH 3/4] block/sed: Check received header lengths

[Jon Derrick]

On 02/15/2017 11:15 AM, Scott Bauer wrote:
> On Wed, Feb 15, 2017 at 12:38:53PM -0700, Jon Derrick wrote:
>> Add a buffer size check against discovery and response header lengths
>> before we loop over their buffers.
>>
>> Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
>> ---
>>  block/sed-opal.c | 35 +++++++++++++++++++++--------------
>>  1 file changed, 21 insertions(+), 14 deletions(-)
>>
>> diff --git a/block/sed-opal.c b/block/sed-opal.c
>> index d6dd604..addf89e 100644
>> --- a/block/sed-opal.c
>> +++ b/block/sed-opal.c
>> @@ -340,10 +340,17 @@ static int opal_discovery0_end(struct opal_dev *dev)
>>  	const struct d0_header *hdr = (struct d0_header *)dev->resp;
>>  	const u8 *epos = dev->resp, *cpos = dev->resp;
>>  	u16 comid = 0;
>> +	u32 hlen = be32_to_cpu(hdr->length);
>>  
>> -	print_buffer(dev->resp, be32_to_cpu(hdr->length));
>> +	print_buffer(dev->resp, hlen);
>>  
>> -	epos += be32_to_cpu(hdr->length); /* end of buffer */
>> +	if (hlen > IO_BUFFER_LENGTH - sizeof(*hdr)) {
>> +		pr_warn("Discovery length overflows buffer (%zu+%u)/%u\n",
>> +			sizeof(*hdr), hlen, IO_BUFFER_LENGTH);
>> +		return -EFAULT;
>> +	}
>> +
>> +	epos += hlen; /* end of buffer */
>>  	cpos += sizeof(*hdr); /* current position on buffer */
>>  
>>  	while (cpos < epos && supported) {
>> @@ -713,6 +720,7 @@ static int response_parse(const u8 *buf, size_t length,
>>  	int total;
>>  	ssize_t token_length;
>>  	const u8 *pos;
>> +	u32 clen, plen, slen;
>>  
>>  	if (!buf)
>>  		return -EFAULT;
>> @@ -724,17 +732,16 @@ static int response_parse(const u8 *buf, size_t length,
>>  	pos = buf;
>>  	pos += sizeof(*hdr);
>>  
>> -	pr_debug("Response size: cp: %d, pkt: %d, subpkt: %d\n",
>> -		 be32_to_cpu(hdr->cp.length),
>> -		 be32_to_cpu(hdr->pkt.length),
>> -		 be32_to_cpu(hdr->subpkt.length));
>> -
>> -	if (hdr->cp.length == 0 || hdr->pkt.length == 0 ||
>> -	    hdr->subpkt.length == 0) {
>> -		pr_err("Bad header length. cp: %d, pkt: %d, subpkt: %d\n",
>> -		       be32_to_cpu(hdr->cp.length),
>> -		       be32_to_cpu(hdr->pkt.length),
>> -		       be32_to_cpu(hdr->subpkt.length));
>> +	clen = be32_to_cpu(hdr->cp.length);
>> +	plen = be32_to_cpu(hdr->pkt.length);
>> +	slen = be32_to_cpu(hdr->subpkt.length);
>> +	pr_debug("Response size: cp: %u, pkt: %u, subpkt: %u\n",
>> +		 clen, plen, slen);
>> +
>> +	if (clen == 0 || plen == 0 || slen == 0 ||
>> +	    (u64)clen + plen + slen > IO_BUFFER_LENGTH) {
> 
> I think we're over calculating here. From my understanding of the spec:
> TCG_Storage_Architecture_Core_Spec_v2.01_r1.00.pdf
> 3.2.3
>   ComPackets, Packets & Subpackets
> 
> The Comp packet size should the size of the packet, and the subpackets.
> The "packet" should be the size of all the subpackets.
> And lastly the subpacket should be the size its payload.
Yep I forgot that. Good catch!


> 
> if ((u64) slen + sizeof(*hdr) > IO_BUFFER_LENGTH)
> 
> Since we never need the com packet length or pkt length (we never use them
> anywhere) I think the above check is okay. Let me know if i'm wrong though,
> or you have a different understanding of the lengths.
Agreed

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