From 4afa5f9617927453ac04b24b584f6c718dfb4f45 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 1 Nov 2015 17:11:19 +0800
Subject: [PATCH] crypto: algif_hash - Only export and import on sockets with data
Git-commit: 4afa5f9617927453ac04b24b584f6c718dfb4f45
Patch-mainline: 4.4-rc1
References: CVE-2016-8646,bsc#1010150

The hash_accept call fails to work on sockets that have not received
any data.  For some algorithm implementations it may cause crashes.

This patch fixes this by ensuring that we only export and import on
sockets that have received data.

Cc: stable@vger.kernel.org
Reported-by: Harsh Jain <harshjain.prof@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Tested-by: Stephan Mueller <smueller@chronox.de>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 crypto/algif_hash.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/crypto/algif_hash.c
+++ b/crypto/algif_hash.c
@@ -187,9 +187,14 @@ static int hash_accept(struct socket *so
 	struct sock *sk2;
 	struct alg_sock *ask2;
 	struct hash_ctx *ctx2;
+	bool more;
 	int err;
 
-	err = crypto_ahash_export(req, state);
+	lock_sock(sk);
+	more = ctx->more;
+	err = more ? crypto_ahash_export(req, state) : 0;
+	release_sock(sk);
+
 	if (err)
 		return err;
 
@@ -200,7 +205,10 @@ static int hash_accept(struct socket *so
 	sk2 = newsock->sk;
 	ask2 = alg_sk(sk2);
 	ctx2 = ask2->private;
-	ctx2->more = 1;
+	ctx2->more = more;
+
+	if (!more)
+		return err;
 
 	err = crypto_ahash_import(&ctx2->req, state);
 	if (err) {
