[CRYPTO] Fix boundary check in standard multi-block cipher processors

The boundary check in the standard multi-block cipher processors are
broken when nbytes is not a multiple of bsize.  In those cases it will
always process an extra block.

This patch corrects the check so that it processes at most nbytes of
data.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

crypto/cipher.c

@@ -191,14 +191,16 @@ static unsigned int cbc_process_encrypt(const struct cipher_desc *desc,
 	u8 *iv = desc->info;
 	unsigned int done = 0;
 
+	nbytes -= bsize;
+
 	do {
 		xor(iv, src);
 		fn(crypto_tfm_ctx(tfm), dst, iv);
 		memcpy(iv, dst, bsize);
 
 		src += bsize;
 		dst += bsize;
-	} while ((done += bsize) < nbytes);
+	} while ((done += bsize) <= nbytes);
 
 	return done;
 }
@@ -219,6 +221,8 @@ static unsigned int cbc_process_decrypt(const struct cipher_desc *desc,
 	u8 *iv = desc->info;
 	unsigned int done = 0;
 
+	nbytes -= bsize;
+
 	do {
 		u8 *tmp_dst = *dst_p;
 
@@ -230,7 +234,7 @@ static unsigned int cbc_process_decrypt(const struct cipher_desc *desc,
 
 		src += bsize;
 		dst += bsize;
-	} while ((done += bsize) < nbytes);
+	} while ((done += bsize) <= nbytes);
 
 	return done;
 }
@@ -243,12 +247,14 @@ static unsigned int ecb_process(const struct cipher_desc *desc, u8 *dst,
 	void (*fn)(void *, u8 *, const u8 *) = desc->crfn;
 	unsigned int done = 0;
 
+	nbytes -= bsize;
+
 	do {
 		fn(crypto_tfm_ctx(tfm), dst, src);
 
 		src += bsize;
 		dst += bsize;
-	} while ((done += bsize) < nbytes);
+	} while ((done += bsize) <= nbytes);
 
 	return done;
 }