[3.13.y-ckt stable] Patch "EVM: Use crypto_memneq() for digest comparisons" has been added to the 3.13.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    EVM: Use crypto_memneq() for digest comparisons

to the linux-3.13.y-queue branch of the 3.13.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11-ckt36.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From f5da00757d5485b21dafa9efe0862b81787671d2 Mon Sep 17 00:00:00 2001
From: Ryan Ware <ware at linux.intel.com>
Date: Thu, 11 Feb 2016 15:58:44 -0800
Subject: EVM: Use crypto_memneq() for digest comparisons

commit 613317bd212c585c20796c10afe5daaa95d4b0a1 upstream.

This patch fixes vulnerability CVE-2016-2085.  The problem exists
because the vm_verify_hmac() function includes a use of memcmp().
Unfortunately, this allows timing side channel attacks; specifically
a MAC forgery complexity drop from 2^128 to 2^12.  This patch changes
the memcmp() to the cryptographically safe crypto_memneq().

Reported-by: Xiaofei Rex Guo <xiaofei.rex.guo at intel.com>
Signed-off-by: Ryan Ware <ware at linux.intel.com>
Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
Signed-off-by: James Morris <james.l.morris at oracle.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 security/integrity/evm/evm_main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 09036f4..c54e14c 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -21,6 +21,7 @@
 #include <linux/integrity.h>
 #include <linux/evm.h>
 #include <crypto/hash.h>
+#include <crypto/algapi.h>
 #include "evm.h"

 int evm_initialized;
@@ -132,7 +133,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 				   xattr_value_len, calc.digest);
 		if (rc)
 			break;
-		rc = memcmp(xattr_data->digest, calc.digest,
+		rc = crypto_memneq(xattr_data->digest, calc.digest,
 			    sizeof(calc.digest));
 		if (rc)
 			rc = -EINVAL;
--
2.7.0