crypto: skcipher - add the ability to abort a skcipher walk

After starting a skcipher walk, the only way to ensure that all
resources it has tied up are released is to complete it. In some
cases, it will be useful to be able to abort a walk cleanly after
it has started, so add this ability to the skcipher walk API.
Signed-off-by: NArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>

include/crypto/internal/skcipher.h

@@ -148,6 +148,11 @@ int skcipher_walk_aead_decrypt(struct skcipher_walk *walk,
 			       struct aead_request *req, bool atomic);
 void skcipher_walk_complete(struct skcipher_walk *walk, int err);
 
+static inline void skcipher_walk_abort(struct skcipher_walk *walk)
+{
+	skcipher_walk_done(walk, -ECANCELED);
+}
+
 static inline void ablkcipher_request_complete(struct ablkcipher_request *req,
 					       int err)
 {