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authorEric Dumazet <edumazet@google.com>2019-03-27 08:21:30 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-17 08:36:46 +0200
commit6996763856e1fb27ccae260e41fd73a3fff56678 (patch)
treea7d4f6375b56d40e809942bfac19dbe782cbef0a
parent9a739f1ad0b12f73afc176b2788c6d0f4e9cc739 (diff)
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 <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>
-rw-r--r--include/net/net_namespace.h1
-rw-r--r--include/net/netns/hash.h15
-rw-r--r--net/core/net_namespace.c1
3 files changed, 4 insertions, 13 deletions
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index c05db6ff2515..0cdafe3935a6 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -53,6 +53,7 @@ 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 69a6715d9f3f..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 <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
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 04fd04ccaa04..4509dec7bd1c 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -282,6 +282,7 @@ 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;
idr_init(&net->netns_ids);