releases/3.10.67/keys-close-race-between-key-lookup-and-freeing.patch

   1 From a3a8784454692dd72e5d5d34dcdab17b4420e74c Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sasha.levin@oracle.com>
   3 Date: Mon, 29 Dec 2014 09:39:01 -0500
   4 Subject: KEYS: close race between key lookup and freeing
   5
   6 From: Sasha Levin <sasha.levin@oracle.com>
   7
   8 commit a3a8784454692dd72e5d5d34dcdab17b4420e74c upstream.
   9
  10 When a key is being garbage collected, it's key->user would get put before
  11 the ->destroy() callback is called, where the key is removed from it's
  12 respective tracking structures.
  13
  14 This leaves a key hanging in a semi-invalid state which leaves a window open
  15 for a different task to try an access key->user. An example is
  16 find_keyring_by_name() which would dereference key->user for a key that is
  17 in the process of being garbage collected (where key->user was freed but
  18 ->destroy() wasn't called yet - so it's still present in the linked list).
  19
  20 This would cause either a panic, or corrupt memory.
  21
  22 Fixes CVE-2014-9529.
  23
  24 Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
  25 Signed-off-by: David Howells <dhowells@redhat.com>
  26 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  27
  28 ---
  29  security/keys/gc.c |    4 ++--
  30  1 file changed, 2 insertions(+), 2 deletions(-)
  31
  32 --- a/security/keys/gc.c
  33 +++ b/security/keys/gc.c
  34 @@ -201,12 +201,12 @@ static noinline void key_gc_unused_keys(
  35                 if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
  36                         atomic_dec(&key->user->nikeys);
  37
  38 -               key_user_put(key->user);
  39 -
  40                 /* now throw away the key memory */
  41                 if (key->type->destroy)
  42                         key->type->destroy(key);
  43
  44 +               key_user_put(key->user);
  45 +
  46                 kfree(key->description);
  47
  48  #ifdef KEY_DEBUGGING