[dpdk-dev] [PATCH v3] lib/rte_rib6: fix stack buffer overflow
Medvedkin, Vladimir
vladimir.medvedkin at intel.com
Thu Jun 24 11:01:16 CEST 2021
Acked-by: Vladimir Medvedkin <vladimir.medvedkin at intel.com>
On 21/06/2021 16:28, 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 | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/lib/rib/rte_rib6.c b/lib/rib/rte_rib6.c
> index f6c55ee45..96424e9c9 100644
> --- a/lib/rib/rte_rib6.c
> +++ b/lib/rib/rte_rib6.c
> @@ -79,20 +79,33 @@ 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
> + * 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 & (UINT8_MAX - 1)) / 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 == RIB6_MAXDEPTH)
> + return NULL;
> +
> return (get_dir(ip, node->depth)) ? node->right : node->left;
> }
>
>
--
Regards,
Vladimir
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