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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org,
        "Herbert Xu" <herbert@gondor.apana.org.au>,
        "syzbot" <syzkaller@googlegroups.com>,
        "Stephan Mueller" <smueller@chronox.de>
Date:   Thu, 07 Jun 2018 15:05:21 +0100
Message-ID: <lsq.1528380321.231153676@decadent.org.uk>
Subject: [PATCH 3.16 120/410] crypto: af_alg - whitelist mask and type
In-Reply-To: <lsq.1528380320.647747352@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stephan Mueller <smueller@chronox.de>

commit bb30b8848c85e18ca7e371d0a869e94b3e383bdf upstream.

The user space interface allows specifying the type and mask field used
to allocate the cipher. Only a subset of the possible flags are intended
for user space. Therefore, white-list the allowed flags.

In case the user space caller uses at least one non-allowed flag, EINVAL
is returned.

Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
[bwh: Backported to 3.16: We don't have a CRYPTO_ALG_INTENRAL flag and
 didn't blacklist it here]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -149,6 +149,7 @@ EXPORT_SYMBOL_GPL(af_alg_release_parent)
 
 static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 {
+	const u32 allowed = CRYPTO_ALG_KERN_DRIVER_ONLY;
 	struct sock *sk = sock->sk;
 	struct alg_sock *ask = alg_sk(sk);
 	struct sockaddr_alg *sa = (void *)uaddr;
@@ -156,6 +157,10 @@ static int alg_bind(struct socket *sock,
 	void *private;
 	int err;
 
+	/* If caller uses non-allowed flag, return error. */
+	if ((sa->salg_feat & ~allowed) || (sa->salg_mask & ~allowed))
+		return -EINVAL;
+
 	if (sock->state == SS_CONNECTED)
 		return -EINVAL;