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Merge branch 'inet-siphash'

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Eric Dumazet says:

====================
inet: use siphash in exception handling

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

I made two distinct patches to help backports, since IPv6
part was added in 4.15
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2021-08-26 10:20:34 +01:00
commit 38d57551dd
2 changed files with 20 additions and 12 deletions
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12
net/ipv4/route.c
View file

@ -600,14 +600,14 @@ static struct fib_nh_exception *fnhe_oldest(struct fnhe_hash_bucket *hash)
return oldest;
}
static inline u32 fnhe_hashfun(__be32 daddr)
static u32 fnhe_hashfun(__be32 daddr)
{
static u32 fnhe_hashrnd __read_mostly;
u32 hval;
static siphash_key_t fnhe_hash_key __read_mostly;
u64 hval;
net_get_random_once(&fnhe_hashrnd, sizeof(fnhe_hashrnd));
hval = jhash_1word((__force u32)daddr, fnhe_hashrnd);
return hash_32(hval, FNHE_HASH_SHIFT);
net_get_random_once(&fnhe_hash_key, sizeof(fnhe_hash_key));
hval = siphash_1u32((__force u32)daddr, &fnhe_hash_key);
return hash_64(hval, FNHE_HASH_SHIFT);
}
static void fill_route_from_fnhe(struct rtable *rt, struct fib_nh_exception *fnhe)

20
net/ipv6/route.c
View file

@ -41,6 +41,7 @@
#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>
@ -1484,17 +1485,24 @@ 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 = jhash2((const u32 *)dst, sizeof(*dst)/sizeof(u32), seed);
net_get_random_once(&rt6_exception_key, sizeof(rt6_exception_key));
#ifdef CONFIG_IPV6_SUBTREES
if (src)
val = jhash2((const u32 *)src, sizeof(*src)/sizeof(u32), 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