[patch 23/76] CRYPTO xcbc: Fix crash with IPsec

[Chris Wright]

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

From: Joy Latten <latten@xxxxxxxxxxxxxx>

[ Upstream commit: 2f40a178e70030c4712fe63807c883f34c3645eb ]

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.

Signed-off-by: Joy Latten <latten@xxxxxxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 crypto/xcbc.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/crypto/xcbc.c
+++ b/crypto/xcbc.c
@@ -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);
 

-- 
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/