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[3.13.y-ckt,stable] Patch "KEYS: Fix race between key destruction and finding a keyring by name" has been added to staging queue

Message ID 1445886651-19587-1-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa Oct. 26, 2015, 7:10 p.m. UTC 
This is a note to let you know that I have just added a patch titled

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

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt29.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

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From 348fce881e2655689ad4cd147cb94ade0d45d590 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Fri, 25 Sep 2015 16:30:08 +0100
Subject: KEYS: Fix race between key destruction and finding a keyring by name

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>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 security/keys/gc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

--
1.9.1
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Patch

diff --git a/security/keys/gc.c b/security/keys/gc.c
index 009d937..38676fa 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -143,6 +143,10 @@  static noinline void key_gc_unused_keys(struct list_head *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 */
@@ -157,10 +161,6 @@  static noinline void key_gc_unused_keys(struct list_head *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);