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crypto: cfb - remove bogus memcpy() with src == dest

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The memcpy() in crypto_cfb_decrypt_inplace() uses walk->iv as both the
source and destination, which has undefined behavior.  It is unneeded
because walk->iv is already used to hold the previous ciphertext block;
thus, walk->iv is already updated to its final value.  So, remove it.

Also, note that in-place decryption is the only case where the previous
ciphertext block is not directly available.  Therefore, as a related
cleanup I also updated crypto_cfb_encrypt_segment() to directly use the
previous ciphertext block rather than save it into walk->iv.  This makes
it consistent with in-place encryption and out-of-place decryption; now
only in-place decryption is different, because it has to be.

Fixes: a7d85e06ed ("crypto: cfb - add support for Cipher FeedBack mode")
Cc: <stable@vger.kernel.org> # v4.17+
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2019-01-03 20:16:11 -08:00 committed by Herbert Xu
parent 394a9e0447
commit 6c2e322b36
1 changed files with 4 additions and 4 deletions
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8
crypto/cfb.c
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@ -77,12 +77,14 @@ static int crypto_cfb_encrypt_segment(struct skcipher_walk *walk,
do { do {
crypto_cfb_encrypt_one(tfm, iv, dst); crypto_cfb_encrypt_one(tfm, iv, dst);
crypto_xor(dst, src, bsize); crypto_xor(dst, src, bsize);
memcpy(iv, dst, bsize); iv = dst;
src += bsize; src += bsize;
dst += bsize; dst += bsize;
} while ((nbytes -= bsize) >= bsize); } while ((nbytes -= bsize) >= bsize);
memcpy(walk->iv, iv, bsize);
return nbytes; return nbytes;
} }
@ -162,7 +164,7 @@ static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
const unsigned int bsize = crypto_cfb_bsize(tfm); const unsigned int bsize = crypto_cfb_bsize(tfm);
unsigned int nbytes = walk->nbytes; unsigned int nbytes = walk->nbytes;
u8 *src = walk->src.virt.addr; u8 *src = walk->src.virt.addr;
u8 *iv = walk->iv; u8 * const iv = walk->iv;
u8 tmp[MAX_CIPHER_BLOCKSIZE]; u8 tmp[MAX_CIPHER_BLOCKSIZE];
do { do {
@ -172,8 +174,6 @@ static int crypto_cfb_decrypt_inplace(struct skcipher_walk *walk,
src += bsize; src += bsize;
} while ((nbytes -= bsize) >= bsize); } while ((nbytes -= bsize) >= bsize);
memcpy(walk->iv, iv, bsize);
return nbytes; return nbytes;
} }