From: Yevgeny Pats <yevgeny@perception-point.io>
Date: Tue, 19 Jan 2016 22:09:04 +0000 (+0000)
Subject: KEYS: Fix keyring ref leak in join_session_keyring()
X-Git-Tag: submit/tizen/20170309.044430~5
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=cb6e9492490f5363fcacabdf4e2341bb33d77c2e;p=profile%2Fwearable%2Fplatform%2Fkernel%2Flinux-3.18-exynos7270.git

KEYS: Fix keyring ref leak in join_session_keyring()

[ Upstream commit 23567fd052a9abb6d67fe8e7a9ccdd9800a540f2 ]

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@perception-point.io>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

[mainline backport of commit d25b4531a808bd0faae3dcd0553421d0570373d1]
Change-Id: I00f47005e93ffb2fe1c68024e9d6820f35ac2602
Signed-off-by: Jaechul Lee <jcsing.lee@samsung.com>
---

diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index bd536cb221e..db91639c81e 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -794,6 +794,7 @@ long join_session_keyring(const char *name)
 		ret = PTR_ERR(keyring);
 		goto error2;
 	} else if (keyring == new->session_keyring) {
+		key_put(keyring);
 		ret = 0;
 		goto error2;
 	}