From 188da790e1f4d164bcfdea486e91fd47e1ba59c5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 27 Mar 2019 08:21:30 -0700 Subject: netns: provide pure entropy for net_hash_mix() commit 355b98553789b646ed97ad801a619ff898471b92 upstream. 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 [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- include/net/net_namespace.h | 2 ++ include/net/netns/hash.h | 17 +++-------------- net/core/net_namespace.c | 1 + 3 files changed, 6 insertions(+), 14 deletions(-) diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index f772dab65474..b3358ba51504 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -54,6 +54,8 @@ struct net { #endif spinlock_t rules_mod_lock; + u32 hash_mix; + struct list_head list; /* list of network namespaces */ struct list_head cleanup_list; /* namespaces on death row */ struct list_head exit_list; /* Use only net_mutex */ diff --git a/include/net/netns/hash.h b/include/net/netns/hash.h index c06ac58ca107..a347b2f9e748 100644 --- a/include/net/netns/hash.h +++ b/include/net/netns/hash.h @@ -1,21 +1,10 @@ #ifndef __NET_NS_HASH_H__ #define __NET_NS_HASH_H__ -#include +#include -struct net; - -static inline unsigned int net_hash_mix(struct net *net) +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 (unsigned)(((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 85b62691f4f2..45ebcc039a68 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -156,6 +156,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns) atomic_set(&net->count, 1); atomic_set(&net->passive, 1); + get_random_bytes(&net->hash_mix, sizeof(u32)); net->dev_base_seq = 1; net->user_ns = user_ns; -- cgit v1.2.3