lkml.org 
[lkml]   [2015]   [Nov]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Date
Subject[PATCH 3.2 59/60] KEYS: Fix race between key destruction and finding a keyring by name
3.2.73-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: David Howells <dhowells@redhat.com>

commit 94c4554ba07adbdde396748ee7ae01e86cf2d8d7 upstream.

There appears to be a race between:

(1) key_gc_unused_keys() which frees key->security and then calls
keyring_destroy() to unlink the name from the name list

(2) find_keyring_by_name() which calls key_permission(), thus accessing
key->security, on a key before checking to see whether the key usage is 0
(ie. the key is dead and might be cleaned up).

Fix this by calling ->destroy() before cleaning up the core key data -
including key->security.

Reported-by: Petr Matousek <pmatouse@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
[carnil: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
security/keys/gc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -172,6 +172,10 @@ static noinline void key_gc_unused_key(s
{
key_check(key);

+ /* Throw away the key data */
+ if (key->type->destroy)
+ key->type->destroy(key);
+
security_key_free(key);

/* deal with the user's key tracking and quota */
@@ -186,10 +190,6 @@ static noinline void key_gc_unused_key(s
if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
atomic_dec(&key->user->nikeys);

- /* now throw away the key memory */
- if (key->type->destroy)
- key->type->destroy(key);
-
key_user_put(key->user);

kfree(key->description);


\
 
 \ /
  Last update: 2015-11-15 03:41    [W:0.392 / U:0.096 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site