From: Eric Dumazet edumazet@google.com
[ Upstream commit 355b98553789b646ed97ad801a619ff898471b92 ]
net_hash_mix() currently uses kernel address of a struct net, and is used in many places that could be used to reveal this address to a patient attacker, thus defeating KASLR, for the typical case (initial net namespace, &init_net is not dynamically allocated)
I believe the original implementation tried to avoid spending too many cycles in this function, but security comes first.
Also provide entropy regardless of CONFIG_NET_NS.
Fixes: 0b4419162aa6 ("netns: introduce the net_hash_mix "salt" for hashes") Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: Amit Klein aksecurity@gmail.com Reported-by: Benny Pinkas benny@pinkas.net Cc: Pavel Emelyanov xemul@openvz.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/net_namespace.h | 1 + include/net/netns/hash.h | 15 ++------------- net/core/net_namespace.c | 1 + 3 files changed, 4 insertions(+), 13 deletions(-)
--- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -56,6 +56,7 @@ struct net { */ spinlock_t rules_mod_lock;
+ u32 hash_mix; atomic64_t cookie_gen;
struct list_head list; /* list of network namespaces */ --- a/include/net/netns/hash.h +++ b/include/net/netns/hash.h @@ -2,21 +2,10 @@ #ifndef __NET_NS_HASH_H__ #define __NET_NS_HASH_H__
-#include <asm/cache.h> - -struct net; +#include <net/net_namespace.h>
static inline u32 net_hash_mix(const struct net *net) { -#ifdef CONFIG_NET_NS - /* - * shift this right to eliminate bits, that are - * always zeroed - */ - - return (u32)(((unsigned long)net) >> L1_CACHE_SHIFT); -#else - return 0; -#endif + return net->hash_mix; } #endif --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -285,6 +285,7 @@ static __net_init int setup_net(struct n
atomic_set(&net->count, 1); refcount_set(&net->passive, 1); + get_random_bytes(&net->hash_mix, sizeof(u32)); net->dev_base_seq = 1; net->user_ns = user_ns; idr_init(&net->netns_ids);