Re: [PATCH v5 5/7] net/eth: Check iovec has enough data earlier

[Philippe Mathieu-Daudé]

On 3/10/21 6:57 PM, Philippe Mathieu-Daudé wrote:
> On 3/10/21 5:53 PM, Stefano Garzarella wrote:
>> On Wed, Mar 10, 2021 at 05:01:33PM +0100, Philippe Mathieu-Daudé wrote:
>>> We want to check fields from ip6_ext_hdr_routing structure
>>> and if correct read the full in6_address. Let's directly check
>>> if our iovec contains enough data for everything, else return
>>> early.
>>>
>>> Suggested-by: Stefano Garzarella <sgarzare@redhat.com>
>>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>>> ---
>>> net/eth.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/net/eth.c b/net/eth.c
>>> index e870d02b0df..28cdc843a69 100644
>>> --- a/net/eth.c
>>> +++ b/net/eth.c
>>> @@ -409,7 +409,7 @@ _eth_get_rss_ex_dst_addr(const struct iovec *pkt,
>>> int pkt_frags,
>>>     size_t input_size = iov_size(pkt, pkt_frags);
>>>     size_t bytes_read;
>>>
>>> -    if (input_size < ext_hdr_offset + sizeof(*ext_hdr)) {
>>> +    if (input_size < ext_hdr_offset + sizeof(*rthdr) +
>>> sizeof(*dst_addr)) {
>>>         return false;
>>>     }
>>
>> If you have to respin, maybe we should also fix the offset in
>> iov_to_buf() in this patch and queue it for stable:
>>
>> @@ -415,7 +415,7 @@ _eth_get_rss_ex_dst_addr(const struct iovec *pkt,
>> int pkt_frags,
>>  
>>      if ((rthdr->rtype == 2) && (rthdr->segleft == 1)) {
>>          bytes_read = iov_to_buf(pkt, pkt_frags,
>> -                                ext_hdr_offset + sizeof(*ext_hdr),
>> +                                ext_hdr_offset + sizeof(*rthdr),
>>                                  dst_addr, sizeof(*dst_addr));
> 
> Oh, so we always screwed the address by 4 bytes...
> 
> This code never worked correctly :(

Confirmed with commit 4555ca6816c ("net: fix incorrect
argument to iov_to_buf") when it then returns incorrect
value until b2caa3b82ed ("net/eth: fix incorrect check
of iov_to_buf() return value") one year later.