releases/4.19.31/crypto-cfb-remove-bogus-memcpy-with-src-dest.patch

   1 From 6c2e322b3621dc8be72e5c86d4fdb587434ba625 Mon Sep 17 00:00:00 2001
   2 From: Eric Biggers <ebiggers@google.com>
   3 Date: Thu, 3 Jan 2019 20:16:11 -0800
   4 Subject: crypto: cfb - remove bogus memcpy() with src == dest
   5
   6 From: Eric Biggers <ebiggers@google.com>
   7
   8 commit 6c2e322b3621dc8be72e5c86d4fdb587434ba625 upstream.
   9
  10 The memcpy() in crypto_cfb_decrypt_inplace() uses walk->iv as both the
  11 source and destination, which has undefined behavior.  It is unneeded
  12 because walk->iv is already used to hold the previous ciphertext block;
  13 thus, walk->iv is already updated to its final value.  So, remove it.
  14
  15 Also, note that in-place decryption is the only case where the previous
  16 ciphertext block is not directly available.  Therefore, as a related
  17 cleanup I also updated crypto_cfb_encrypt_segment() to directly use the
  18 previous ciphertext block rather than save it into walk->iv.  This makes
  19 it consistent with in-place encryption and out-of-place decryption; now
  20 only in-place decryption is different, because it has to be.
  21
  22 Fixes: a7d85e06ed80 ("crypto: cfb - add support for Cipher FeedBack mode")
  23 Cc: <stable@vger.kernel.org> # v4.17+
  24 Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
  25 Signed-off-by: Eric Biggers <ebiggers@google.com>
  26 Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
  27 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  28
  29 ---
  30  crypto/cfb.c |    8 ++++----
  31  1 file changed, 4 insertions(+), 4 deletions(-)
  32
  33 --- a/crypto/cfb.c
  34 +++ b/crypto/cfb.c
  35 @@ -77,12 +77,14 @@ static int crypto_cfb_encrypt_segment(st
  36         do {
  37                 crypto_cfb_encrypt_one(tfm, iv, dst);
  38                 crypto_xor(dst, src, bsize);
  39 -               memcpy(iv, dst, bsize);
  40 +               iv = dst;
  41
  42                 src += bsize;
  43                 dst += bsize;
  44         } while ((nbytes -= bsize) >= bsize);
  45
  46 +       memcpy(walk->iv, iv, bsize);
  47 +
  48         return nbytes;
  49  }
  50
  51 @@ -162,7 +164,7 @@ static int crypto_cfb_decrypt_inplace(st
  52         const unsigned int bsize = crypto_cfb_bsize(tfm);
  53         unsigned int nbytes = walk->nbytes;
  54         u8 *src = walk->src.virt.addr;
  55 -       u8 *iv = walk->iv;
  56 +       u8 * const iv = walk->iv;
  57         u8 tmp[MAX_CIPHER_BLOCKSIZE];
  58
  59         do {
  60 @@ -172,8 +174,6 @@ static int crypto_cfb_decrypt_inplace(st
  61                 src += bsize;
  62         } while ((nbytes -= bsize) >= bsize);
  63
  64 -       memcpy(walk->iv, iv, bsize);
  65 -
  66         return nbytes;
  67  }
  68