queue-3.18/netns-provide-pure-entropy-for-net_hash_mix.patch

   1 From foo@baz Mon Apr 15 07:47:06 CEST 2019
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Wed, 27 Mar 2019 08:21:30 -0700
   4 Subject: netns: provide pure entropy for net_hash_mix()
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8 [ Upstream commit 355b98553789b646ed97ad801a619ff898471b92 ]
   9
  10 net_hash_mix() currently uses kernel address of a struct net,
  11 and is used in many places that could be used to reveal this
  12 address to a patient attacker, thus defeating KASLR, for
  13 the typical case (initial net namespace, &init_net is
  14 not dynamically allocated)
  15
  16 I believe the original implementation tried to avoid spending
  17 too many cycles in this function, but security comes first.
  18
  19 Also provide entropy regardless of CONFIG_NET_NS.
  20
  21 Fixes: 0b4419162aa6 ("netns: introduce the net_hash_mix "salt" for hashes")
  22 Signed-off-by: Eric Dumazet <edumazet@google.com>
  23 Reported-by: Amit Klein <aksecurity@gmail.com>
  24 Reported-by: Benny Pinkas <benny@pinkas.net>
  25 Cc: Pavel Emelyanov <xemul@openvz.org>
  26 Signed-off-by: David S. Miller <davem@davemloft.net>
  27 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  28 ---
  29  include/net/net_namespace.h |    2 ++
  30  include/net/netns/hash.h    |   15 ++-------------
  31  net/core/net_namespace.c    |    1 +
  32  3 files changed, 5 insertions(+), 13 deletions(-)
  33
  34 --- a/include/net/net_namespace.h
  35 +++ b/include/net/net_namespace.h
  36 @@ -54,6 +54,8 @@ struct net {
  37  #endif
  38         spinlock_t              rules_mod_lock;
  39
  40 +       u32                     hash_mix;
  41 +
  42         struct list_head        list;           /* list of network namespaces */
  43         struct list_head        cleanup_list;   /* namespaces on death row */
  44         struct list_head        exit_list;      /* Use only net_mutex */
  45 --- a/include/net/netns/hash.h
  46 +++ b/include/net/netns/hash.h
  47 @@ -1,21 +1,10 @@
  48  #ifndef __NET_NS_HASH_H__
  49  #define __NET_NS_HASH_H__
  50
  51 -#include <asm/cache.h>
  52 -
  53 -struct net;
  54 +#include <net/net_namespace.h>
  55
  56  static inline unsigned int net_hash_mix(struct net *net)
  57  {
  58 -#ifdef CONFIG_NET_NS
  59 -       /*
  60 -        * shift this right to eliminate bits, that are
  61 -        * always zeroed
  62 -        */
  63 -
  64 -       return (unsigned)(((unsigned long)net) >> L1_CACHE_SHIFT);
  65 -#else
  66 -       return 0;
  67 -#endif
  68 +       return net->hash_mix;
  69  }
  70  #endif
  71 --- a/net/core/net_namespace.c
  72 +++ b/net/core/net_namespace.c
  73 @@ -156,6 +156,7 @@ static __net_init int setup_net(struct n
  74
  75         atomic_set(&net->count, 1);
  76         atomic_set(&net->passive, 1);
  77 +       get_random_bytes(&net->hash_mix, sizeof(u32));
  78         net->dev_base_seq = 1;
  79         net->user_ns = user_ns;
  80