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authorEric Dumazet <edumazet@google.com>2019-03-27 08:21:30 -0700
committerBen Hutchings <ben@decadent.org.uk>2019-07-09 22:04:22 +0100
commit188da790e1f4d164bcfdea486e91fd47e1ba59c5 (patch)
parenta62393d7eb63bd075c51154002825cc7ab4dd3eb (diff)
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 <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>
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 {
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 <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)
- /*
- * shift this right to eliminate bits, that are
- * always zeroed
- */
- return (unsigned)(((unsigned long)net) >> L1_CACHE_SHIFT);
- return 0;
+ return net->hash_mix;
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;