Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1753914AbcDRCem (ORCPT <rfc822;w@1wt.eu>);
	Sun, 17 Apr 2016 22:34:42 -0400
Received: from mail.linuxfoundation.org ([140.211.169.12]:36280 "EHLO
	mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751413AbcDRCej (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Sun, 17 Apr 2016 22:34:39 -0400
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, stable@vger.kernel.org,
        Nicolai Stange <nicstange@gmail.com>,
        Herbert Xu <herbert@gondor.apana.org.au>
Subject: [PATCH 4.4 002/137] PKCS#7: pkcs7_validate_trust(): initialize the _trusted output argument
Date: Mon, 18 Apr 2016 11:27:44 +0900
Message-Id: <20160418022507.512674913@linuxfoundation.org>
X-Mailer: git-send-email 2.8.0
In-Reply-To: <20160418022507.236379264@linuxfoundation.org>
References: <20160418022507.236379264@linuxfoundation.org>
User-Agent: quilt/0.64
MIME-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-15
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2349
Lines: 65

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Nicolai Stange <nicstange@gmail.com>

commit e54358915d0a00399c11c2c23ae1be674cba188a upstream.

Despite what the DocBook comment to pkcs7_validate_trust() says, the
*_trusted argument is never set to false.

pkcs7_validate_trust() only positively sets *_trusted upon encountering
a trusted PKCS#7 SignedInfo block.

This is quite unfortunate since its callers, system_verify_data() for
example, depend on pkcs7_validate_trust() clearing *_trusted on non-trust.

Indeed, UBSAN splats when attempting to load the uninitialized local
variable 'trusted' from system_verify_data() in pkcs7_validate_trust():

  UBSAN: Undefined behaviour in crypto/asymmetric_keys/pkcs7_trust.c:194:14
  load of value 82 is not a valid value for type '_Bool'
  [...]
  Call Trace:
    [<ffffffff818c4d35>] dump_stack+0xbc/0x117
    [<ffffffff818c4c79>] ? _atomic_dec_and_lock+0x169/0x169
    [<ffffffff8194113b>] ubsan_epilogue+0xd/0x4e
    [<ffffffff819419fa>] __ubsan_handle_load_invalid_value+0x111/0x158
    [<ffffffff819418e9>] ? val_to_string.constprop.12+0xcf/0xcf
    [<ffffffff818334a4>] ? x509_request_asymmetric_key+0x114/0x370
    [<ffffffff814b83f0>] ? kfree+0x220/0x370
    [<ffffffff818312c2>] ? public_key_verify_signature_2+0x32/0x50
    [<ffffffff81835e04>] pkcs7_validate_trust+0x524/0x5f0
    [<ffffffff813c391a>] system_verify_data+0xca/0x170
    [<ffffffff813c3850>] ? top_trace_array+0x9b/0x9b
    [<ffffffff81510b29>] ? __vfs_read+0x279/0x3d0
    [<ffffffff8129372f>] mod_verify_sig+0x1ff/0x290
    [...]

The implication is that pkcs7_validate_trust() effectively grants trust
when it really shouldn't have.

Fix this by explicitly setting *_trusted to false at the very beginning
of pkcs7_validate_trust().

Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 crypto/asymmetric_keys/pkcs7_trust.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -178,6 +178,8 @@ int pkcs7_validate_trust(struct pkcs7_me
 	int cached_ret = -ENOKEY;
 	int ret;
 
+	*_trusted = false;
+
 	for (p = pkcs7->certs; p; p = p->next)
 		p->seen = false;