crypto: salsa20 - don't access already-freed walk.iv

commit edaf28e996af69222b2cb40455dbb5459c2b875a upstream.

If the user-provided IV needs to be aligned to the algorithm's
alignmask, then skcipher_walk_virt() copies the IV into a new aligned
buffer walk.iv.  But skcipher_walk_virt() can fail afterwards, and then
if the caller unconditionally accesses walk.iv, it's a use-after-free.

salsa20-generic doesn't set an alignmask, so currently it isn't affected
by this despite unconditionally accessing walk.iv.  However this is more
subtle than desired, and it was actually broken prior to the alignmask
being removed by commit b62b3db76f73 ("crypto: salsa20-generic - cleanup
and convert to skcipher API").

Since salsa20-generic does not update the IV and does not need any IV
alignment, update it to use req->iv instead of walk.iv.

Fixes: 2407d60872dd ("[CRYPTO] salsa20: Salsa20 stream cipher")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/crypto/salsa20_generic.c b/crypto/salsa20_generic.c
index 00fce32ae17af9fa630db24e2ff2ee4f8b7bf547..1d7ad0256fd3b5c4ddf96d018954c606e7c3ed07 100644 (file)
--- a/crypto/salsa20_generic.c
+++ b/crypto/salsa20_generic.c
@@ -161,7 +161,7 @@ static int salsa20_crypt(struct skcipher_request *req)
 
        err = skcipher_walk_virt(&walk, req, false);
 
-       salsa20_init(state, ctx, walk.iv);
+       salsa20_init(state, ctx, req->iv);
 
        while (walk.nbytes > 0) {
                unsigned int nbytes = walk.nbytes;