linux-kernel - [PATCH 4.19 129/280] crypto: pcbc - remove bogus memcpy()s with src == dest

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Message-Id: <20190322111316.371999296@linuxfoundation.org>
Date:   Fri, 22 Mar 2019 12:14:42 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, David Howells <dhowells@...hat.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH 4.19 129/280] crypto: pcbc - remove bogus memcpy()s with src == dest

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

------------------

From: Eric Biggers <ebiggers@...gle.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@...r.kernel.org> # v2.6.21+
Cc: David Howells <dhowells@...hat.com>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -51,7 +51,7 @@ 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[MAX_CIPHER_BLOCKSIZE];
 
 	do {
@@ -84,8 +84,6 @@ static int crypto_pcbc_encrypt_inplace(s
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
@@ -121,7 +119,7 @@ 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);
@@ -132,8 +130,6 @@ static int crypto_pcbc_decrypt_segment(s
 		dst += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }
 
@@ -144,7 +140,7 @@ 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[MAX_CIPHER_BLOCKSIZE] __aligned(__alignof__(u32));
 
 	do {
@@ -156,8 +152,6 @@ static int crypto_pcbc_decrypt_inplace(s
 		src += bsize;
 	} while ((nbytes -= bsize) >= bsize);
 
-	memcpy(walk->iv, iv, bsize);
-
 	return nbytes;
 }