[v2] lib/rte_rib6: fix stack buffer overflow
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Commit Message
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(-)
Comments
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 ?
> +
> + /*
> + * 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.
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.
>
@@ -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
+ * 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;
+
+ /*
+ * 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;
return (get_dir(ip, node->depth)) ? node->right : node->left;
}