netdev - [PATCH]kernel crashes when using aes-xcbc-mac with IPsec

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Message-Id: <200803051451.m25EpKv8016389@faith.austin.ibm.com>
Date:	Wed, 5 Mar 2008 08:51:20 -0600
From:	Joy Latten <latten@...tin.ibm.com>
To:	linux-crypto@...r.kernel
Cc:	davem@...emloft.net, herbert@...dor.apana.org.au,
	netdev@...r.kernel.org
Subject: [PATCH]kernel crashes when using aes-xcbc-mac with IPsec 

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.
Please let me know if it looks ok.

regards,
Joy 

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

diff -urpN net-2.6.26/crypto/xcbc.c net-2.6.26.patch/crypto/xcbc.c
--- net-2.6.26/crypto/xcbc.c	2008-03-04 16:11:32.000000000 -0600
+++ net-2.6.26.patch/crypto/xcbc.c	2008-03-04 18:28:51.000000000 -0600
@@ -124,6 +124,11 @@ static int crypto_xcbc_digest_update2(st
 		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 = crypto_kmap(pg, 0) + offset;
@@ -177,7 +182,6 @@ static int crypto_xcbc_digest_update2(st
 			offset = 0;
 			pg++;
 		}
-		nbytes-=sg[i].length;
 		i++;
 	} while (nbytes>0);
 
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