[PATCH 3.16 024/129] crypto: pcbc - remove bogus memcpy()s with src == dest

[Ben Hutchings]

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Eric Biggers <ebigg...@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: David Howells <dhowe...@redhat.com>
Signed-off-by: Eric Biggers <ebigg...@google.com>
Signed-off-by: Herbert Xu <herb...@gondor.apana.org.au>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
 crypto/pcbc.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

--- a/crypto/pcbc.c
+++ b/crypto/pcbc.c
@@ -52,7 +52,7 @@ 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);
@@ -76,7 +76,7 @@ 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 {
@@ -89,8 +89,6 @@ static int crypto_pcbc_encrypt_inplace(s
                src += bsize;
        } while ((nbytes -= bsize) >= bsize);
 
-       memcpy(walk->iv, iv, bsize);
-
        return nbytes;
 }
 
@@ -130,7 +128,7 @@ 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 {
                fn(crypto_cipher_tfm(tfm), dst, src);
@@ -142,8 +140,6 @@ static int crypto_pcbc_decrypt_segment(s
                dst += bsize;
        } while ((nbytes -= bsize) >= bsize);
 
-       memcpy(walk->iv, iv, bsize);
-
        return nbytes;
 }
 
@@ -156,7 +152,7 @@ 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];
 
        do {
@@ -169,8 +165,6 @@ static int crypto_pcbc_decrypt_inplace(s
                src += bsize;
        } while ((nbytes -= bsize) >= bsize);
 
-       memcpy(walk->iv, iv, bsize);
-
        return nbytes;
 }