[PATCH 3.16 120/410] crypto: af_alg - whitelist mask and type

[Ben Hutchings]

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

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

From: Stephan Mueller <smueller@xxxxxxxxxx>

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@xxxxxxxxxxxxxxxx>
Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
[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@xxxxxxxxxxxxxxx>
---
--- 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;