net/mlx5e: CT, Fix coverity issue

The cited commit introduced the following coverity issue at function
mlx5_tc_ct_rule_to_tuple_nat:
- Memory - corruptions (OVERRUN)
  Overrunning array "tuple->ip.src_v6.in6_u.u6_addr32" of 4 4-byte
  elements at element index 7 (byte offset 31) using index
  "ip6_offset" (which evaluates to 7).

In case of IPv6 destination address rewrite, ip6_offset values are
between 4 to 7, which will cause memory overrun of array
"tuple->ip.src_v6.in6_u.u6_addr32" to array
"tuple->ip.dst_v6.in6_u.u6_addr32".

Fixed by writing the value directly to array
"tuple->ip.dst_v6.in6_u.u6_addr32" in case ip6_offset values are
between 4 to 7.

Fixes: bc562be9 ("net/mlx5e: CT: Save ct entries tuples in hashtables")
Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.c

@@ -246,8 +246,10 @@ mlx5_tc_ct_rule_to_tuple_nat(struct mlx5_ct_tuple *tuple,
 		case FLOW_ACT_MANGLE_HDR_TYPE_IP6:
 			ip6_offset = (offset - offsetof(struct ipv6hdr, saddr));
 			ip6_offset /= 4;
-			if (ip6_offset < 8)
+			if (ip6_offset < 4)
 				tuple->ip.src_v6.s6_addr32[ip6_offset] = cpu_to_be32(val);
+			else if (ip6_offset < 8)
+				tuple->ip.dst_v6.s6_addr32[ip6_offset - 4] = cpu_to_be32(val);
 			else
 				return -EOPNOTSUPP;
 			break;