crypto: ahash - Fix EINPROGRESS notification callback

The ahash API modifies the request's callback function in order
to clean up after itself in some corner cases (unaligned final
and missing finup).

When the request is complete ahash will restore the original
callback and everything is fine. However, when the request gets
an EBUSY on a full queue, an EINPROGRESS callback is made while
the request is still ongoing.

In this case the ahash API will incorrectly call its own callback.

This patch fixes the problem by creating a temporary request
object on the stack which is used to relay EINPROGRESS back to
the original completion function.

This patch also adds code to preserve the original flags value.

Fixes: ab6bf4e5e5e4 ("crypto: hash - Fix the pointer voodoo in...")
Cc: <[e-mail]>
Reported-by: Sabrina Dubroca <[e-mail]>
Tested-by: Sabrina Dubroca <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

crypto/ahash.c

···
 	crypto_completion_t complete;
 	void *data;
 	u8 *result;
+	u32 flags;
 	void *ubuf[] CRYPTO_MINALIGN_ATTR;
 };
 
···
 	priv->result = req->result;
 	priv->complete = req->base.complete;
 	priv->data = req->base.data;
+	priv->flags = req->base.flags;
+
 	/*
 	 * WARNING: We do not backup req->priv here! The req->priv
 	 *          is for internal use of the Crypto API and the
···
 	return 0;
 }
 
-static void ahash_restore_req(struct ahash_request *req)
+static void ahash_restore_req(struct ahash_request *req, int err)
 {
 	struct ahash_request_priv *priv = req->priv;
 
+	if (!err)
+		memcpy(priv->result, req->result,
+		       crypto_ahash_digestsize(crypto_ahash_reqtfm(req)));
+
 	/* Restore the original crypto request. */
 	req->result = priv->result;
-	req->base.complete = priv->complete;
-	req->base.data = priv->data;
+
+	ahash_request_set_callback(req, priv->flags,
+				   priv->complete, priv->data);
 	req->priv = NULL;
 
 	/* Free the req->priv.priv from the ADJUSTED request. */
 	kzfree(priv);
 }
 
-static void ahash_op_unaligned_finish(struct ahash_request *req, int err)
+static void ahash_notify_einprogress(struct ahash_request *req)
 {
 	struct ahash_request_priv *priv = req->priv;
+	struct crypto_async_request oreq;
 
-	if (err == -EINPROGRESS)
-		return;
+	oreq.data = priv->data;
 
-	if (!err)
-		memcpy(priv->result, req->result,
-		       crypto_ahash_digestsize(crypto_ahash_reqtfm(req)));
-
-	ahash_restore_req(req);
+	priv->complete(&oreq, -EINPROGRESS);
 }
 
 static void ahash_op_unaligned_done(struct crypto_async_request *req, int err)
 {
 	struct ahash_request *areq = req->data;
+
+	if (err == -EINPROGRESS) {
+		ahash_notify_einprogress(areq);
+		return;
+	}
 
 	/*
 	 * Restore the original request, see ahash_op_unaligned() for what
···
 	 */
 
 	/* First copy req->result into req->priv.result */
-	ahash_op_unaligned_finish(areq, err);
+	ahash_restore_req(areq, err);
 
 	/* Complete the ORIGINAL request. */
 	areq->base.complete(&areq->base, err);
···
 		return err;
 
 	err = op(req);
-	ahash_op_unaligned_finish(req, err);
+	if (err == -EINPROGRESS ||
+	    (err == -EBUSY && (ahash_request_flags(req) &
+			       CRYPTO_TFM_REQ_MAY_BACKLOG)))
+		return err;
+
+	ahash_restore_req(req, err);
 
 	return err;
 }
···
 }
 EXPORT_SYMBOL_GPL(crypto_ahash_digest);
 
-static void ahash_def_finup_finish2(struct ahash_request *req, int err)
-{
-	struct ahash_request_priv *priv = req->priv;
-
-	if (err == -EINPROGRESS)
-		return;
-
-	if (!err)
-		memcpy(priv->result, req->result,
-		       crypto_ahash_digestsize(crypto_ahash_reqtfm(req)));
-
-	ahash_restore_req(req);
-}
-
 static void ahash_def_finup_done2(struct crypto_async_request *req, int err)
 {
 	struct ahash_request *areq = req->data;
 
-	ahash_def_finup_finish2(areq, err);
+	if (err == -EINPROGRESS)
+		return;
+
+	ahash_restore_req(areq, err);
 
 	areq->base.complete(&areq->base, err);
 }
···
 		goto out;
 
 	req->base.complete = ahash_def_finup_done2;
-	req->base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
+
 	err = crypto_ahash_reqtfm(req)->final(req);
+	if (err == -EINPROGRESS ||
+	    (err == -EBUSY && (ahash_request_flags(req) &
+			       CRYPTO_TFM_REQ_MAY_BACKLOG)))
+		return err;
 
 out:
-	ahash_def_finup_finish2(req, err);
+	ahash_restore_req(req, err);
 	return err;
 }
 
···
 {
 	struct ahash_request *areq = req->data;
 
+	if (err == -EINPROGRESS) {
+		ahash_notify_einprogress(areq);
+		return;
+	}
+
+	areq->base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
+
 	err = ahash_def_finup_finish1(areq, err);
+	if (areq->priv)
+		return;
 
 	areq->base.complete(&areq->base, err);
 }
···
 		return err;
 
 	err = tfm->update(req);
+	if (err == -EINPROGRESS ||
+	    (err == -EBUSY && (ahash_request_flags(req) &
+			       CRYPTO_TFM_REQ_MAY_BACKLOG)))
+		return err;
+
 	return ahash_def_finup_finish1(req, err);
 }
 

include/crypto/internal/hash.h

···
 	return crypto_alloc_instance2(name, alg, ahash_instance_headroom());
 }
 
+static inline void ahash_request_complete(struct ahash_request *req, int err)
+{
+	req->base.complete(&req->base, err);
+}
+
+static inline u32 ahash_request_flags(struct ahash_request *req)
+{
+	return req->base.flags;
+}
+
 static inline struct crypto_ahash *crypto_spawn_ahash(
 	struct crypto_ahash_spawn *spawn)
 {