linux-kernel - [PATCH 2/3] KEYS: Change the name of the dead type to ".dead" to prevent user access

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 19 Apr 2017 17:08:20 +0100
From:   David Howells <dhowells@...hat.com>
To:     jmorris@...ei.org
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        dhowells@...hat.com, keyrings@...r.kernel.org,
        torvalds@...ux-foundation.org, linux-kernel-modules@...r.kernel.org
Subject: [PATCH 2/3] KEYS: Change the name of the dead type to ".dead" to
 prevent user access

This fixes CVE-2017-6951.

Userspace should not be able to do things with the "dead" key type as it
doesn't have some of the helper functions set upon it that the kernel
needs.  Attempting to use it may cause the kernel to crash.

Fix this by changing the name of the type to ".dead" so that it's rejected
up front on userspace syscalls by key_get_type_from_user().

Though this doesn't seem to affect recent kernels, it does affect older
ones, certainly those prior to:

	commit c06cfb08b88dfbe13be44a69ae2fdc3a7c902d81
	Author: David Howells <dhowells@...hat.com>
	Date:   Tue Sep 16 17:36:06 2014 +0100
	KEYS: Remove key_type::match in favour of overriding default by match_preparse

which went in before 3.18-rc1.

Signed-off-by: David Howells <dhowells@...hat.com>
cc: stable@...r.kernel.org
---

 security/keys/gc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/security/keys/gc.c b/security/keys/gc.c
index addf060399e0..9cb4fe4478a1 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -46,7 +46,7 @@ static unsigned long key_gc_flags;
  * immediately unlinked.
  */
 struct key_type key_type_dead = {
-	.name = "dead",
+	.name = ".dead",
 };
 
 /*