[PATCH v4.9] crypto: pcbc - remove bogus memcpy()s with src == dest

[Maxim Zhukov <crazycdeveloper@gmail.com>]

From: Eric Biggers <ebiggers@google.com>

commit 251b7aea34ba3c4d4fdfa9447695642eb8b8b098 upstream

The memcpy()s in the PCBC implementation use walk->iv as both the source
and destination, which has undefined behavior.  These memcpy()'s are
actually unneeded, because walk->iv is already used to hold the previous
plaintext block XOR'd with the previous ciphertext block.  Thus,
walk->iv is already updated to its final value.

So remove the broken and unnecessary memcpy()s.

Fixes: 91652be5d1b9 ("[CRYPTO] pcbc: Add Propagated CBC template")
Cc: <stable@vger.kernel.org> # v2.6.21+
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Maxim Zhukov <mussitantesmortem@gmail.com>
---
 crypto/pcbc.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/crypto/pcbc.c b/crypto/pcbc.c
index f654965f0933..de81f716cf26 100644
--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -52,7 +52,7 @@ static int crypto_pcbc_encrypt_segment(struct blkcipher_desc *desc,
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
-	u8 *iv = walk->iv;
+	u8 * const iv = walk->iv;
 
 	do {
 		crypto_xor(iv, src, bsize);
@@ -76,7 +76,7 @@ static int crypto_pcbc_encrypt_inplace(struct blkcipher_desc *desc,
 	int bsize = crypto_cipher_blocksize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
-	u8 *iv = walk->iv;
+	u8 * const iv = walk->iv;
 	u8 tmpbuf[bsize];
 
 	do {
@@ -89,8 +89,6 @@ static int crypto_pcbc_encrypt_inplace(struct blkcipher_desc *desc,
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
@@ -130,7 +128,7 @@ static int crypto_pcbc_decrypt_segment(struct blkcipher_desc *desc,
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
 	u8 *dst = walk->dst.virt.addr;
-	u8 *iv = walk->iv;
+	u8 * const iv = walk->iv;
 
 	do {
 		fn(crypto_cipher_tfm(tfm), dst, src);
@@ -142,8 +140,6 @@ static int crypto_pcbc_decrypt_segment(struct blkcipher_desc *desc,
 		dst += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
@@ -156,7 +152,7 @@ static int crypto_pcbc_decrypt_inplace(struct blkcipher_desc *desc,
 	int bsize = crypto_cipher_blocksize(tfm);
 	unsigned int nbytes = walk->nbytes;
 	u8 *src = walk->src.virt.addr;
-	u8 *iv = walk->iv;
+	u8 * const iv = walk->iv;
 	u8 tmpbuf[bsize];
 
 	do {
@@ -169,8 +165,6 @@ static int crypto_pcbc_decrypt_inplace(struct blkcipher_desc *desc,
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
-- 
2.21.0