releases/4.19.35/netns-provide-pure-entropy-for-net_hash_mix.patch

   1 From 21da00dd528b93c6d3a6f107a53d3ba48a991bfe Mon Sep 17 00:00:00 2001
   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 [ Upstream commit 355b98553789b646ed97ad801a619ff898471b92 ]
   7
   8 net_hash_mix() currently uses kernel address of a struct net,
   9 and is used in many places that could be used to reveal this
  10 address to a patient attacker, thus defeating KASLR, for
  11 the typical case (initial net namespace, &init_net is
  12 not dynamically allocated)
  13
  14 I believe the original implementation tried to avoid spending
  15 too many cycles in this function, but security comes first.
  16
  17 Also provide entropy regardless of CONFIG_NET_NS.
  18
  19 Fixes: 0b4419162aa6 ("netns: introduce the net_hash_mix "salt" for hashes")
  20 Signed-off-by: Eric Dumazet <edumazet@google.com>
  21 Reported-by: Amit Klein <aksecurity@gmail.com>
  22 Reported-by: Benny Pinkas <benny@pinkas.net>
  23 Cc: Pavel Emelyanov <xemul@openvz.org>
  24 Signed-off-by: David S. Miller <davem@davemloft.net>
  25 Signed-off-by: Sasha Levin <sashal@kernel.org>
  26 ---
  27  include/net/net_namespace.h |  1 +
  28  include/net/netns/hash.h    | 10 ++--------
  29  net/core/net_namespace.c    |  1 +
  30  3 files changed, 4 insertions(+), 8 deletions(-)
  31
  32 diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
  33 index 9b5fdc50519a..3f7b166262d7 100644
  34 --- a/include/net/net_namespace.h
  35 +++ b/include/net/net_namespace.h
  36 @@ -57,6 +57,7 @@ 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 diff --git a/include/net/netns/hash.h b/include/net/netns/hash.h
  45 index 16a842456189..d9b665151f3d 100644
  46 --- a/include/net/netns/hash.h
  47 +++ b/include/net/netns/hash.h
  48 @@ -2,16 +2,10 @@
  49  #ifndef __NET_NS_HASH_H__
  50  #define __NET_NS_HASH_H__
  51
  52 -#include <asm/cache.h>
  53 -
  54 -struct net;
  55 +#include <net/net_namespace.h>
  56
  57  static inline u32 net_hash_mix(const struct net *net)
  58  {
  59 -#ifdef CONFIG_NET_NS
  60 -       return (u32)(((unsigned long)net) >> ilog2(sizeof(*net)));
  61 -#else
  62 -       return 0;
  63 -#endif
  64 +       return net->hash_mix;
  65  }
  66  #endif
  67 diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
  68 index 670c84b1bfc2..7320f0844a50 100644
  69 --- a/net/core/net_namespace.c
  70 +++ b/net/core/net_namespace.c
  71 @@ -304,6 +304,7 @@ static __net_init int setup_net(struct net *net, struct user_namespace *user_ns)
  72
  73         refcount_set(&net->count, 1);
  74         refcount_set(&net->passive, 1);
  75 +       get_random_bytes(&net->hash_mix, sizeof(u32));
  76         net->dev_base_seq = 1;
  77         net->user_ns = user_ns;
  78         idr_init(&net->netns_ids);
  79 --
  80 2.19.1
  81