Re: [dpdk-dev] [PATCH] lpm: fix buffer overflow

["Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>]

Hi David,

On 20/10/2021 21:55, David Marchand wrote:
> Hello Vladimir,
> 
> On Fri, Oct 8, 2021 at 11:29 PM Vladimir Medvedkin
> <vladimir.medvedkin@intel.com> wrote:
>>
>> This patch fixes buffer overflow reported by ASAN,
>> please reference https://bugs.dpdk.org/show_bug.cgi?id=819
>>
>> The rte_lpm6 keeps routing information for control plane purpose
>> inside the rte_hash table which uses rte_jhash() as a hash function.
>>  From the rte_jhash() documentation: If input key is not aligned to
>> four byte boundaries or a multiple of four bytes in length,
>> the memory region just after may be read (but not used in the
>> computation).
>> rte_lpm6 uses 17 bytes keys consisting of IPv6 address (16 bytes) +
>> depth (1 byte).
>>
>> This patch increases the size of the depth field up to uint32_t
>> and sets the alignment to 4 bytes.
>>
>> Bugzilla ID: 819
>> Fixes: 86b3b21952a8 ("lpm6: store rules in hash table")
>> Cc: alex@therouter.net
>> Cc: stable@dpdk.org
> 
> This change should be internal, and not breaking ABI, but are we sure
> we want to backport it?
> 

I think yes, I don't see any reason why we should not backport it.
Do you think we should not?

> 
>>
>> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
>> ---
>>   lib/lpm/rte_lpm6.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/lib/lpm/rte_lpm6.c b/lib/lpm/rte_lpm6.c
>> index 37baabb..d5e0918 100644
>> --- a/lib/lpm/rte_lpm6.c
>> +++ b/lib/lpm/rte_lpm6.c
>> @@ -80,8 +80,8 @@ struct rte_lpm6_rule {
>>   /** Rules tbl entry key. */
>>   struct rte_lpm6_rule_key {
>>          uint8_t ip[RTE_LPM6_IPV6_ADDR_SIZE]; /**< Rule IP address. */
>> -       uint8_t depth; /**< Rule depth. */
>> -};
>> +       uint32_t depth; /**< Rule depth. */
>> +} __rte_aligned(sizeof(uint32_t));
> 
> I would recommend doing the same than for hash tests: keep growing
> depth to 32bits, but no enforcement of alignment and add build check
> on structure size being sizeof(uin32_t) aligned.
> 

Agree, will send v2

> 
>>
>>   /* Header of tbl8 */
>>   struct rte_lpm_tbl8_hdr {
>> --
>> 2.7.4
>>
> 
> 

-- 
Regards,
Vladimir