[dpdk-dev] [PATCH v2] lib/rte_rib6: fix stack buffer overflow

[Medvedkin, Vladimir]

Hi Owen,

Just a few nits inlined below

On 16/06/2021 21:18, ohilyard at iol.unh.edu wrote:
> From: Owen Hilyard <ohilyard at 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 at 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 ?

> +
> +	/*
> +	 * 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 at dpdk.org on v3 to 
backport this patch.

Apart from that LGTM.

-- 
Regards,
Vladimir