queue-4.14/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 |    1 +
  30  include/net/netns/hash.h    |   15 ++-------------
  31  net/core/net_namespace.c    |    1 +
  32  3 files changed, 4 insertions(+), 13 deletions(-)
  33
  34 --- a/include/net/net_namespace.h
  35 +++ b/include/net/net_namespace.h
  36 @@ -56,6 +56,7 @@ struct net {
  37                                                  */
  38         spinlock_t              rules_mod_lock;
  39
  40 +       u32                     hash_mix;
  41         atomic64_t              cookie_gen;
  42
  43         struct list_head        list;           /* list of network namespaces */
  44 --- a/include/net/netns/hash.h
  45 +++ b/include/net/netns/hash.h
  46 @@ -2,21 +2,10 @@
  47  #ifndef __NET_NS_HASH_H__
  48  #define __NET_NS_HASH_H__
  49
  50 -#include <asm/cache.h>
  51 -
  52 -struct net;
  53 +#include <net/net_namespace.h>
  54
  55  static inline u32 net_hash_mix(const struct net *net)
  56  {
  57 -#ifdef CONFIG_NET_NS
  58 -       /*
  59 -        * shift this right to eliminate bits, that are
  60 -        * always zeroed
  61 -        */
  62 -
  63 -       return (u32)(((unsigned long)net) >> L1_CACHE_SHIFT);
  64 -#else
  65 -       return 0;
  66 -#endif
  67 +       return net->hash_mix;
  68  }
  69  #endif
  70 --- a/net/core/net_namespace.c
  71 +++ b/net/core/net_namespace.c
  72 @@ -285,6 +285,7 @@ static __net_init int setup_net(struct n
  73
  74         atomic_set(&net->count, 1);
  75         refcount_set(&net->passive, 1);
  76 +       get_random_bytes(&net->hash_mix, sizeof(u32));
  77         net->dev_base_seq = 1;
  78         net->user_ns = user_ns;
  79         idr_init(&net->netns_ids);