From: Eric Dumazet edumazet@google.com

commit 4785305c05b25a242e5314cc821f54ade4c18810 upstream.

A group of security researchers brought to our attention the weakness of hash function used in rt6_exception_hash()

Lets use siphash instead of Jenkins Hash, to considerably reduce security risks.

Following patch deals with IPv4.

Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: Keyu Man kman001@ucr.edu Cc: Wei Wang weiwan@google.com Cc: Martin KaFai Lau kafai@fb.com Acked-by: Wei Wang weiwan@google.com Signed-off-by: David S. Miller davem@davemloft.net [OP: adjusted context for 4.19 stable] Signed-off-by: Ovidiu Panait ovidiu.panait@windriver.com --- net/ipv6/route.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c index f884739a0c1c..9bc806a4ded6 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -45,6 +45,7 @@ #include <linux/nsproxy.h> #include <linux/slab.h> #include <linux/jhash.h> +#include <linux/siphash.h> #include <net/net_namespace.h> #include <net/snmp.h> #include <net/ipv6.h> @@ -1337,17 +1338,24 @@ static void rt6_exception_remove_oldest(struct rt6_exception_bucket *bucket) static u32 rt6_exception_hash(const struct in6_addr *dst, const struct in6_addr *src) { - static u32 seed __read_mostly; - u32 val; + static siphash_key_t rt6_exception_key __read_mostly; + struct { + struct in6_addr dst; + struct in6_addr src; + } __aligned(SIPHASH_ALIGNMENT) combined = { + .dst = *dst, + }; + u64 val;

- net_get_random_once(&seed, sizeof(seed)); - val = jhash(dst, sizeof(*dst), seed); + net_get_random_once(&rt6_exception_key, sizeof(rt6_exception_key));

#ifdef CONFIG_IPV6_SUBTREES if (src) - val = jhash(src, sizeof(*src), val); + combined.src = *src; #endif - return hash_32(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT); + val = siphash(&combined, sizeof(combined), &rt6_exception_key); + + return hash_64(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT); }

/* Helper function to find the cached rt in the hash table