crypto: krb5enc - fix async decrypt skipping hash verification

krb5enc_dispatch_decrypt() sets req->base.complete as the skcipher
callback, which is the caller's own completion handler. When the
skcipher completes asynchronously, this signals "done" to the caller
without executing krb5enc_dispatch_decrypt_hash(), completely bypassing
the integrity verification (hash check).

Compare with the encrypt path which correctly uses
krb5enc_encrypt_done as an intermediate callback to chain into the
hash computation on async completion.

Fix by adding krb5enc_decrypt_done as an intermediate callback that
chains into krb5enc_dispatch_decrypt_hash() upon async skcipher
completion, matching the encrypt path's callback pattern.

Also fix EBUSY/EINPROGRESS handling throughout: remove
krb5enc_request_complete() which incorrectly swallowed EINPROGRESS
notifications that must be passed up to callers waiting on backlogged
requests, and add missing EBUSY checks in krb5enc_encrypt_ahash_done
for the dispatch_encrypt return value.

Fixes: d1775a1 ("crypto: Add 'krb5enc' hash and cipher AEAD algorithm")
Signed-off-by: Dudu Lu <phx0fer@gmail.com>

Unset MAY_BACKLOG on the async completion path so the user won't
see back-to-back EINPROGRESS notifications.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: phx0fer

crypto/krb5enc.c

@@ -39,12 +39,6 @@ struct krb5enc_request_ctx {
 	char tail[];
 };
 
-static void krb5enc_request_complete(struct aead_request *req, int err)
-{
-	if (err != -EINPROGRESS)
-		aead_request_complete(req, err);
-}
-
 /**
  * crypto_krb5enc_extractkeys - Extract Ke and Ki keys from the key blob.
  * @keys: Where to put the key sizes and pointers
@@ -127,7 +121,7 @@ static void krb5enc_encrypt_done(void *data, int err)
 {
 	struct aead_request *req = data;
 
-	krb5enc_request_complete(req, err);
+	aead_request_complete(req, err);
 }
 
 /*
@@ -188,14 +182,16 @@ static void krb5enc_encrypt_ahash_done(void *data, int err)
 	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff);
 
 	if (err)
-		return krb5enc_request_complete(req, err);
+		goto out;
 
 	krb5enc_insert_checksum(req, ahreq->result);
 
-	err = krb5enc_dispatch_encrypt(req,
-				       aead_request_flags(req) & ~CRYPTO_TFM_REQ_MAY_SLEEP);
-	if (err != -EINPROGRESS)
-		aead_request_complete(req, err);
+	err = krb5enc_dispatch_encrypt(req, 0);
+	if (err == -EINPROGRESS)
+		return;
+
+out:
+	aead_request_complete(req, err);
 }
 
 /*
@@ -265,17 +261,16 @@ static void krb5enc_decrypt_hash_done(void *data, int err)
 {
 	struct aead_request *req = data;
 
-	if (err)
-		return krb5enc_request_complete(req, err);
-
-	err = krb5enc_verify_hash(req);
-	krb5enc_request_complete(req, err);
+	if (!err)
+		err = krb5enc_verify_hash(req);
+	aead_request_complete(req, err);
 }
 
 /*
  * Dispatch the hashing of the plaintext after we've done the decryption.
  */
-static int krb5enc_dispatch_decrypt_hash(struct aead_request *req)
+static int krb5enc_dispatch_decrypt_hash(struct aead_request *req,
+					 unsigned int flags)
 {
 	struct crypto_aead *krb5enc = crypto_aead_reqtfm(req);
 	struct aead_instance *inst = aead_alg_instance(krb5enc);
@@ -291,7 +286,7 @@ static int krb5enc_dispatch_decrypt_hash(struct aead_request *req)
 	ahash_request_set_tfm(ahreq, auth);
 	ahash_request_set_crypt(ahreq, req->dst, hash,
 				req->assoclen + req->cryptlen - authsize);
-	ahash_request_set_callback(ahreq, aead_request_flags(req),
+	ahash_request_set_callback(ahreq, flags,
 				   krb5enc_decrypt_hash_done, req);
 
 	err = crypto_ahash_digest(ahreq);
@@ -301,6 +296,21 @@ static int krb5enc_dispatch_decrypt_hash(struct aead_request *req)
 	return krb5enc_verify_hash(req);
 }
 
+static void krb5enc_decrypt_done(void *data, int err)
+{
+	struct aead_request *req = data;
+
+	if (err)
+		goto out;
+
+	err = krb5enc_dispatch_decrypt_hash(req, 0);
+	if (err == -EINPROGRESS)
+		return;
+
+out:
+	aead_request_complete(req, err);
+}
+
 /*
  * Dispatch the decryption of the ciphertext.
  */
@@ -324,7 +334,7 @@ static int krb5enc_dispatch_decrypt(struct aead_request *req)
 
 	skcipher_request_set_tfm(skreq, ctx->enc);
 	skcipher_request_set_callback(skreq, aead_request_flags(req),
-				      req->base.complete, req->base.data);
+				      krb5enc_decrypt_done, req);
 	skcipher_request_set_crypt(skreq, src, dst,
 				   req->cryptlen - authsize, req->iv);
 
@@ -339,7 +349,7 @@ static int krb5enc_decrypt(struct aead_request *req)
 	if (err < 0)
 		return err;
 
-	return krb5enc_dispatch_decrypt_hash(req);
+	return krb5enc_dispatch_decrypt_hash(req, aead_request_flags(req));
 }
 
 static int krb5enc_init_tfm(struct crypto_aead *tfm)