From adbb8bdd392db14dc80ad1ac29f8f1d37ab57a62 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 27 Mar 2019 08:21:30 -0700 Subject: [PATCH] netns: provide pure entropy for net_hash_mix() [ 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 Reported-by: Amit Klein Reported-by: Benny Pinkas Cc: Pavel Emelyanov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- 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(-) diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index f4bf75fac349..d96c9d9cca96 100644 --- 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 */ diff --git a/include/net/netns/hash.h b/include/net/netns/hash.h index 24c78183a4c2..d9b665151f3d 100644 --- 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 - -struct net; +#include 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 diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index 0dd6359e5924..60b88718b1d4 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -285,6 +285,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns) 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); -- 2.20.1