From: Herbert Xu <herbert.xu@redhat.com>
Date: Thu, 6 Mar 2008 20:06:36 +0800
Subject: [crypto] xcbc: fix IPsec crash with aes-xcbc-mac
Message-id: 20080306120636.GA7558@gondor.apana.org.au
O-Subject: [RHEL5.2 PATCH] [CRYPTO] xcbc: Fix IPsec crash with aes-xcbc-mac
Bugzilla: 435377

Hi:

RHEL5.2 BZ 435377

This patch fixes a crash that prevents the XCBC algorithm from
being used with IPsec.  This is a problem since it is a required
algorithm.

This patch has been accepted upstream.  Please ack,

From: Joy Latten <latten@austin.ibm.com>

When using aes-xcbc-mac for authentication in IPsec,
the kernel crashes. It seems this algorithm doesn't
account for the space IPsec may make in scatterlist for authtag.
Thus when crypto_xcbc_digest_update2() gets called,
nbytes may be less than sg[i].length.
Since nbytes is an unsigned number, it wraps
at the end of the loop allowing us to go back
into loop and causing crash in memcpy.

I used update function in digest.c to model this fix.

Signed-off-by: Joy Latten <latten@austin.ibm.com>

Acked-by: Thomas Graf <tgraf@redhat.com>
Acked-by: "David S. Miller" <davem@redhat.com>

diff --git a/crypto/xcbc.c b/crypto/xcbc.c
index b730c6f..e822111 100644
--- a/crypto/xcbc.c
+++ b/crypto/xcbc.c
@@ -124,6 +124,11 @@ static int crypto_xcbc_digest_update2(struct hash_desc *pdesc,
 		unsigned int offset = sg[i].offset;
 		unsigned int slen = sg[i].length;
 
+		if (unlikely(slen > nbytes))
+			slen = nbytes;
+
+		nbytes -= slen;
+
 		while (slen > 0) {
 			unsigned int len = min(slen, ((unsigned int)(PAGE_SIZE)) - offset);
 			char *p = ncrypto_kmap(pg, 0) + offset;
@@ -177,7 +182,6 @@ static int crypto_xcbc_digest_update2(struct hash_desc *pdesc,
 			offset = 0;
 			pg++;
 		}
-		nbytes-=sg[i].length;
 		i++;
 	} while (nbytes>0);