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 <stable@xxxxxxxxxxxxxxx> know about it.
>From 94c4554ba07adbdde396748ee7ae01e86cf2d8d7 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@xxxxxxxxxx>
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 <dhowells@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
security/keys/gc.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -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 dhowells@xxxxxxxxxx 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
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