From 251b7aea34ba3c4d4fdfa9447695642eb8b8b098 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers@google.com>
Date: Thu, 3 Jan 2019 20:16:13 -0800
Subject: [PATCH] crypto: pcbc - remove bogus memcpy()s with src == dest
Git-commit: 251b7aea34ba3c4d4fdfa9447695642eb8b8b098
Patch-mainline: v5.1-rc1
References: bsc#1051510

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>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 crypto/pcbc.c |   14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -50,7 +50,7 @@ static int crypto_pcbc_encrypt_segment(s
 	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);
@@ -72,7 +72,7 @@ static int crypto_pcbc_encrypt_inplace(s
 	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 {
@@ -85,8 +85,6 @@ static int crypto_pcbc_encrypt_inplace(s
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
@@ -122,7 +120,7 @@ static int crypto_pcbc_decrypt_segment(s
 	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_cipher_decrypt_one(tfm, dst, src);
@@ -134,8 +132,6 @@ static int crypto_pcbc_decrypt_segment(s
 		dst += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
@@ -146,7 +142,7 @@ static int crypto_pcbc_decrypt_inplace(s
 	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] __aligned(__alignof__(u32));
 
 	do {
@@ -159,8 +155,6 @@ static int crypto_pcbc_decrypt_inplace(s
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }