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Commit a1c2f322 authored by Eric Dumazet's avatar Eric Dumazet Committed by Greg Kroah-Hartman
Browse files

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: 0b441916 ("netns: introduce the net_hash_mix "salt" for hashes")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarAmit Klein <aksecurity@gmail.com>
Reported-by: default avatarBenny Pinkas <benny@pinkas.net>
Cc: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 53a19068

include/net/net_namespace.h

+1 −0
Original line number Diff line number Diff line
@@ -57,6 +57,7 @@ struct net { 
						 */

	spinlock_t		rules_mod_lock;



	u32			hash_mix;

	atomic64_t		cookie_gen;



	struct list_head	list;		/* list of network namespaces */

include/net/netns/hash.h

+2 −8
Original line number Diff line number Diff line
@@ -2,16 +2,10 @@ 
#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

	return (u32)(((unsigned long)net) >> ilog2(sizeof(*net)));

#else

	return 0;

#endif

	return net->hash_mix;

}

#endif

net/core/net_namespace.c

+1 −0
Original line number Diff line number Diff line
@@ -304,6 +304,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns) 


	refcount_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);