Patch "KEYS: Fix race between key destruction and finding a keyring by name" has been added to the 3.10-stable tree

This is a note to let you know that I've just added the patch titled

KEYS: Fix race between key destruction and finding a keyring by name

to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
keys-fix-race-between-key-destruction-and-finding-a-keyring-by-name.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: David Howells <[email protected]>
Date: Fri, 25 Sep 2015 16:30:08 +0100
Subject: KEYS: Fix race between key destruction and finding a keyring by name

From: David Howells <[email protected]>

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.

---
 security/keys/gc.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

@@ -187,6 +187,10 @@ static noinline void key_gc_unused_keys(
 		kdebug("- %u", key->serial);
 		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 */

@@ -201,10 +205,6 @@ static noinline void key_gc_unused_keys(
 		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);

Patches currently in stable-queue which might be from [email protected] are

queue-3.10/keys-fix-keyring-ref-leak-in-join_session_keyring.patch queue-3.10/keys-fix-crash-when-attempt-to-garbage-collect-an-uninstantiated-keyring.patch queue-3.10/keys-fix-race-between-read-and-revoke.patch queue-3.10/keys-fix-race-between-key-destruction-and-finding-a-keyring-by-name.patch queue-3.10/keys-refcount-bug-fix.patch queue-3.10/keys-prevent-keys-from-being-removed-from-specified-keyrings.patch