linux-kernel - Re: [PATCH] KEYS: Fix keyring ref leak in join_session

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Message-ID: <20160120082039.GA22945@kroah.com>
Date:	Wed, 20 Jan 2016 00:20:39 -0800
From:	Greg KH <gregkh@...uxfoundation.org>
To:	David Howells <dhowells@...hat.com>
Cc:	jmorris@...ei.org, Don Zickus <dzickus@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Yevgeny Pats <yevgeny@...ception-point.io>,
	linux-kernel@...r.kernel.org, Jarod Wilson <jarod@...hat.com>,
	linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH] KEYS: Fix keyring ref leak in join_session_keyring()

On Tue, Jan 19, 2016 at 10:09:04PM +0000, David Howells wrote:
> From: Yevgeny Pats <yevgeny@...ception-point.io>
> 
> This fixes CVE-2016-0728.
> 
> If a thread is asked to join as a session keyring the keyring that's already
> set as its session, we leak a keyring reference.
> 
> This can be tested with the following program:
> 
> 	#include <stddef.h>
> 	#include <stdio.h>
> 	#include <sys/types.h>
> 	#include <keyutils.h>
> 
> 	int main(int argc, const char *argv[])
> 	{
> 		int i = 0;
> 		key_serial_t serial;
> 
> 		serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
> 				"leaked-keyring");
> 		if (serial < 0) {
> 			perror("keyctl");
> 			return -1;
> 		}
> 
> 		if (keyctl(KEYCTL_SETPERM, serial,
> 			   KEY_POS_ALL | KEY_USR_ALL) < 0) {
> 			perror("keyctl");
> 			return -1;
> 		}
> 
> 		for (i = 0; i < 100; i++) {
> 			serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
> 					"leaked-keyring");
> 			if (serial < 0) {
> 				perror("keyctl");
> 				return -1;
> 			}
> 		}
> 
> 		return 0;
> 	}
> 
> If, after the program has run, there something like the following line in
> /proc/keys:
> 
> 3f3d898f I--Q---   100 perm 3f3f0000     0     0 keyring   leaked-keyring: empty
> 
> with a usage count of 100 * the number of times the program has been run,
> then the kernel is malfunctioning.  If leaked-keyring has zero usages or
> has been garbage collected, then the problem is fixed.
> 
> Reported-by: Yevgeny Pats <yevgeny@...ception-point.io>
> Signed-off-by: David Howells <dhowells@...hat.com>
> Acked-by: Don Zickus <dzickus@...hat.com>
> Acked-by: Prarit Bhargava <prarit@...hat.com>
> Acked-by: Jarod Wilson <jarod@...hat.com>

Any reason you didn't tag this for stable kernels?

thanks,

greg k-h