3.16.70-rc1 review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
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 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 [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- 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 */ --- 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 <asm/cache.h> +#include <net/net_namespace.h>
-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 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -156,6 +156,7 @@ static __net_init int setup_net(struct n
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;