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From: "Medvedkin, Vladimir" <vladimir.medvedkin@intel.com>
To: ohilyard@iol.unh.edu
Cc: dev@dpdk.org, stephen@networkplumber.org, david.marchand@redhat.com
References: <20210616160730.348523-1-ohilyard@iol.unh.edu>
<20210616181833.356159-1-ohilyard@iol.unh.edu>
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Date: Fri, 18 Jun 2021 19:27:26 +0300
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Subject: Re: [dpdk-dev] [PATCH v2] lib/rte_rib6: fix stack buffer overflow
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On 18/06/2021 19:22, Medvedkin, Vladimir wrote:
> Hi Owen,
>
> Just a few nits inlined below
>
> On 16/06/2021 21:18, ohilyard@iol.unh.edu wrote:
>> From: Owen Hilyard <ohilyard@iol.unh.edu>
>>
>> ASAN found a stack buffer overflow in lib/rib/rte_rib6.c:get_dir.
>> The fix for the stack buffer overflow was to make sure depth
>> was always < 128, since when depth = 128 it caused the index
>> into the ip address to be 16, which read off the end of the array.
>>
>> While trying to solve the buffer overflow, I noticed that a few
>> changes could be made to remove the for loop entirely.
>>
>> Fixes: f7e861e21c ("rib: support IPv6")
>>
>> Signed-off-by: Owen Hilyard <ohilyard@iol.unh.edu>
>> ---
>> lib/rib/rte_rib6.c | 27 +++++++++++++++++++--------
>> 1 file changed, 19 insertions(+), 8 deletions(-)
>>
>> diff --git a/lib/rib/rte_rib6.c b/lib/rib/rte_rib6.c
>> index f6c55ee45..a4daf12ca 100644
>> --- a/lib/rib/rte_rib6.c
>> +++ b/lib/rib/rte_rib6.c
>> @@ -79,20 +79,31 @@ is_covered(const uint8_t
>> ip1[RTE_RIB6_IPV6_ADDR_SIZE],
>> static inline int
>> get_dir(const uint8_t ip[RTE_RIB6_IPV6_ADDR_SIZE], uint8_t depth)
>> {
>> - int i = 0;
>> - uint8_t p_depth, msk;
>> -
>> - for (p_depth = depth; p_depth >= 8; p_depth -= 8)
>> - i++;
>> -
>> - msk = 1 << (7 - p_depth);
>> - return (ip[i] & msk) != 0;
>> + uint8_t index, msk;
>> +
>> + /* depth & 127 clamps depth to values that will not
>
> Please be consistent with the coding style. Check 1.3.1 in
> https://doc.dpdk.org/guides/contributing/coding_style.html
>
>> + * read off the end of ip.
>> + * depth is the number of bits deep into ip to traverse, and
>> + * is incremented in blocks of 8 (1 byte). This means the last
>> + * 3 bits are irrelevant to what the index of ip should be.
>> + */
>> + index = (depth & 127) >> 3;
>
> (depth & INT8_MAX) / UINT8_MAX ?
Ugh...
sed 's/UINT8_MAX/CHAR_BIT'
>
>> +
>> + /*
>> + * msk is the bitmask used to extract the bit used to decide the
>> + * direction of the next step of the binary search.
>> + */
>> + msk = 1 << (7 - (depth & 7));
>> +
>> + return (ip[index] & msk) != 0;
>> }
>> static inline struct rte_rib6_node *
>> get_nxt_node(struct rte_rib6_node *node,
>> const uint8_t ip[RTE_RIB6_IPV6_ADDR_SIZE])
>> {
>> + if (node->depth == 128)
>> + return NULL;
>
> please use RIB6_MAXDEPTH instead of 128.
> Also I'd put a blank line before the final return.
>
>> return (get_dir(ip, node->depth)) ? node->right : node->left;
>> }
>>
>
> while this is a bug fix, please add Cc: stable@dpdk.org on v3 to
> backport this patch.
>
> Apart from that LGTM.
>
--
Regards,
Vladimir