[3.8.y.z extended stable] Patch "crypto: ansi_cprng - Fix off by one error in non-block size request" has been added to staging queue

[Kamal Mostafa]

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

    crypto: ansi_cprng - Fix off by one error in non-block size request

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.19.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From c2d0ba8f7dc98fced1464788f6ef3ce3fdcbede9 Mon Sep 17 00:00:00 2001
From: Neil Horman <nhorman at tuxdriver.com>
Date: Tue, 17 Sep 2013 08:33:11 -0400
Subject: crypto: ansi_cprng - Fix off by one error in non-block size request

commit 714b33d15130cbb5ab426456d4e3de842d6c5b8a upstream.

Stephan Mueller reported to me recently a error in random number generation in
the ansi cprng. If several small requests are made that are less than the
instances block size, the remainder for loop code doesn't increment
rand_data_valid in the last iteration, meaning that the last bytes in the
rand_data buffer gets reused on the subsequent smaller-than-a-block request for
random data.

The fix is pretty easy, just re-code the for loop to make sure that
rand_data_valid gets incremented appropriately

Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
Reported-by: Stephan Mueller <stephan.mueller at atsec.com>
CC: Stephan Mueller <stephan.mueller at atsec.com>
CC: Petr Matousek <pmatouse at redhat.com>
CC: Herbert Xu <herbert at gondor.apana.org.au>
CC: "David S. Miller" <davem at davemloft.net>
Signed-off-by: Herbert Xu <herbert at gondor.apana.org.au>
[ kamal: 3.8-stable for CVE-2013-4345 ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 crypto/ansi_cprng.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index c0bb377..666f196 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -230,11 +230,11 @@ remainder:
 	 */
 	if (byte_count < DEFAULT_BLK_SZ) {
 empty_rbuf:
-		for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
-			ctx->rand_data_valid++) {
+		while (ctx->rand_data_valid < DEFAULT_BLK_SZ) {
 			*ptr = ctx->rand_data[ctx->rand_data_valid];
 			ptr++;
 			byte_count--;
+			ctx->rand_data_valid++;
 			if (byte_count == 0)
 				goto done;
 		}
--
1.8.3.2