[4.2.y-ckt stable] Patch "KEYS: Don't permit request_key() to construct a new keyring" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    KEYS: Don't permit request_key() to construct a new keyring

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

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

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From c404b4f7a0ba58b2397c54b4408348ffae91d317 Mon Sep 17 00:00:00 2001
From: David Howells <dhowells at redhat.com>
Date: Mon, 19 Oct 2015 11:20:28 +0100
Subject: KEYS: Don't permit request_key() to construct a new keyring

commit 911b79cde95c7da0ec02f48105358a36636b7a71 upstream.

If request_key() is used to find a keyring, only do the search part - don't
do the construction part if the keyring was not found by the search.  We
don't really want keyrings in the negative instantiated state since the
rejected/negative instantiation error value in the payload is unioned with
keyring metadata.

Now the kernel gives an error:

	request_key("keyring", "#selinux,bdekeyring", "keyring", KEY_SPEC_USER_SESSION_KEYRING) = -1 EPERM (Operation not permitted)

Signed-off-by: David Howells <dhowells at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 security/keys/request_key.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 486ef6f..0d62531 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -440,6 +440,9 @@ static struct key *construct_key_and_link(struct keyring_search_context *ctx,

 	kenter("");

+	if (ctx->index_key.type == &key_type_keyring)
+		return ERR_PTR(-EPERM);
+
 	user = key_user_lookup(current_fsuid());
 	if (!user)
 		return ERR_PTR(-ENOMEM);
--
1.9.1