1 files changed, 24 insertions, 51 deletions

diff --git a/crypto/algif_skcipher.c b/crypto/algif_skcipher.c
index ba0a17fd95ac..35ebc3e0201b 100644
--- a/crypto/algif_skcipher.c
+++ b/crypto/algif_skcipher.c
@@ -79,20 +79,6 @@ static int algif_skcipher_export(struct sock *sk, struct skcipher_request *req)
 	return err;
 }
 
-static void algif_skcipher_done(void *data, int err)
-{
-	struct af_alg_async_req *areq = data;
-	struct sock *sk = areq->sk;
-
-	if (err)
-		goto out;
-
-	err = algif_skcipher_export(sk, &areq->cra_u.skcipher_req);
-
-out:
-	af_alg_async_cb(data, err);
-}
-
 static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
 			     size_t ignored, int flags)
 {
@@ -171,43 +157,30 @@ static int _skcipher_recvmsg(struct socket *sock, struct msghdr *msg,
 		cflags |= CRYPTO_SKCIPHER_REQ_CONT;
 	}
 
-	if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
-		/* AIO operation */
-		sock_hold(sk);
-		areq->iocb = msg->msg_iocb;
-
-		/* Remember output size that will be generated. */
-		areq->outlen = len;
-
-		skcipher_request_set_callback(&areq->cra_u.skcipher_req,
-					      cflags |
-					      CRYPTO_TFM_REQ_MAY_SLEEP,
-					      algif_skcipher_done, areq);
-		err = ctx->enc ?
-			crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
-			crypto_skcipher_decrypt(&areq->cra_u.skcipher_req);
-
-		/* AIO operation in progress */
-		if (err == -EINPROGRESS)
-			return -EIOCBQUEUED;
-
-		sock_put(sk);
-	} else {
-		/* Synchronous operation */
-		skcipher_request_set_callback(&areq->cra_u.skcipher_req,
-					      cflags |
-					      CRYPTO_TFM_REQ_MAY_SLEEP |
-					      CRYPTO_TFM_REQ_MAY_BACKLOG,
-					      crypto_req_done, &ctx->wait);
-		err = crypto_wait_req(ctx->enc ?
-			crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
-			crypto_skcipher_decrypt(&areq->cra_u.skcipher_req),
-						 &ctx->wait);
-
-		if (!err)
-			err = algif_skcipher_export(
-				sk, &areq->cra_u.skcipher_req);
-	}
+	/*
+	 * Force synchronous processing.  The async (AIO) path passed the
+	 * socket-wide ctx->iv into the request, which the worker
+	 * dereferenced after the socket lock had been dropped, letting a
+	 * concurrent sendmsg(ALG_SET_IV) inject an attacker IV.  Mainline
+	 * removed the AIO socket path in commit fcc77d33a34c ("net: Remove
+	 * support for AIO on sockets"); the minimal stable fix is to always
+	 * complete synchronously, so ctx->iv is only ever dereferenced under
+	 * the socket lock.  This also keeps the IV chaining intact: for
+	 * ciphers with statesize == 0 (e.g. ctr, cbc) the chained IV is
+	 * carried by the req->iv writeback into ctx->iv, which is only
+	 * consistent on the synchronous path.
+	 */
+	skcipher_request_set_callback(&areq->cra_u.skcipher_req,
+				      cflags |
+				      CRYPTO_TFM_REQ_MAY_SLEEP |
+				      CRYPTO_TFM_REQ_MAY_BACKLOG,
+				      crypto_req_done, &ctx->wait);
+	err = crypto_wait_req(ctx->enc ?
+		crypto_skcipher_encrypt(&areq->cra_u.skcipher_req) :
+		crypto_skcipher_decrypt(&areq->cra_u.skcipher_req),
+				 &ctx->wait);
+	if (!err)
+		err = algif_skcipher_export(sk, &areq->cra_u.skcipher_req);
 
 free:
 	af_alg_free_resources(areq);