linux-kernel - [PATCH 3.2 4/4] keys: Guard against null match function in keyring_search

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Message-ID: <lsq.1491052673.768763980@decadent.org.uk>
Date:   Sat, 01 Apr 2017 14:17:53 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Igor Redko" <redkoi@...tuozzo.com>,
        "David Howells" <dhowells@...hat.com>,
        "Andrey Ryabinin" <aryabinin@...tuozzo.com>,
        "idl3r" <idler1984@...il.com>
Subject: [PATCH 3.2 4/4] keys: Guard against null match function in
 keyring_search_aux()

3.2.88-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Ben Hutchings <ben@...adent.org.uk>

The "dead" key type has no match operation, and a search for keys of
this type can cause a null dereference in keyring_search_aux().
keyring_search() has a check for this, but request_keyring_and_link()
does not.  Move the check into keyring_search_aux(), covering both of
them.

This was fixed upstream by commit c06cfb08b88d ("KEYS: Remove
key_type::match in favour of overriding default by match_preparse"),
part of a series of large changes that are not suitable for
backporting.

CVE-2017-2647 / CVE-2017-6951

Reported-by: Igor Redko <redkoi@...tuozzo.com>
Reported-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
References: https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-2647
Reported-by: idl3r <idler1984@...il.com>
References: https://www.spinics.net/lists/keyrings/msg01845.html
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Cc: David Howells <dhowells@...hat.com>
---
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -336,6 +336,9 @@ key_ref_t keyring_search_aux(key_ref_t k
 	if (keyring->type != &key_type_keyring)
 		goto error;
 
+	if (!match)
+		return ERR_PTR(-ENOKEY);
+
 	rcu_read_lock();
 
 	now = current_kernel_time();
@@ -484,9 +487,6 @@ key_ref_t keyring_search(key_ref_t keyri
 			 struct key_type *type,
 			 const char *description)
 {
-	if (!type->match)
-		return ERR_PTR(-ENOKEY);
-
 	return keyring_search_aux(keyring, current->cred,
 				  type, description, type->match, false);
 }