queue-4.19/crypto-salsa20-don-t-access-already-freed-walk.iv.patch

   1 From edaf28e996af69222b2cb40455dbb5459c2b875a Mon Sep 17 00:00:00 2001
   2 From: Eric Biggers <ebiggers@google.com>
   3 Date: Tue, 9 Apr 2019 23:46:30 -0700
   4 Subject: crypto: salsa20 - don't access already-freed walk.iv
   5
   6 From: Eric Biggers <ebiggers@google.com>
   7
   8 commit edaf28e996af69222b2cb40455dbb5459c2b875a upstream.
   9
  10 If the user-provided IV needs to be aligned to the algorithm's
  11 alignmask, then skcipher_walk_virt() copies the IV into a new aligned
  12 buffer walk.iv.  But skcipher_walk_virt() can fail afterwards, and then
  13 if the caller unconditionally accesses walk.iv, it's a use-after-free.
  14
  15 salsa20-generic doesn't set an alignmask, so currently it isn't affected
  16 by this despite unconditionally accessing walk.iv.  However this is more
  17 subtle than desired, and it was actually broken prior to the alignmask
  18 being removed by commit b62b3db76f73 ("crypto: salsa20-generic - cleanup
  19 and convert to skcipher API").
  20
  21 Since salsa20-generic does not update the IV and does not need any IV
  22 alignment, update it to use req->iv instead of walk.iv.
  23
  24 Fixes: 2407d60872dd ("[CRYPTO] salsa20: Salsa20 stream cipher")
  25 Cc: stable@vger.kernel.org
  26 Signed-off-by: Eric Biggers <ebiggers@google.com>
  27 Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
  28 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  29
  30 ---
  31  crypto/salsa20_generic.c |    2 +-
  32  1 file changed, 1 insertion(+), 1 deletion(-)
  33
  34 --- a/crypto/salsa20_generic.c
  35 +++ b/crypto/salsa20_generic.c
  36 @@ -161,7 +161,7 @@ static int salsa20_crypt(struct skcipher
  37
  38         err = skcipher_walk_virt(&walk, req, true);
  39
  40 -       salsa20_init(state, ctx, walk.iv);
  41 +       salsa20_init(state, ctx, req->iv);
  42
  43         while (walk.nbytes > 0) {
  44                 unsigned int nbytes = walk.nbytes;