Commit ccd5fbba authored by Eric Dumazet's avatar Eric Dumazet Committed by DidntRead
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: 0b4419162aa6 ("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 avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cef948c4

include/net/net_namespace.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

include/net/netns/hash.h

+2 −13
Original line number Diff line number Diff line 
#ifndef __NET_NS_HASH_H__

#define __NET_NS_HASH_H__



#include <asm/cache.h>



struct net;

#include <net/net_namespace.h>



static inline unsigned int net_hash_mix(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

net/core/net_namespace.c

+1 −0
Original line number Diff line number Diff line
@@ -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;