crypto: af_alg - whitelist mask and type

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>
Cc: <stable@vger.kernel.org>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 6 insertions, 4 deletions

diff --git a/crypto/af_alg.c b/crypto/af_alg.c
index 35d4dcea381f..5231f421ad00 100644
--- a/crypto/af_alg.c
+++ b/crypto/af_alg.c
@@ -150,7 +150,7 @@ EXPORT_SYMBOL_GPL(af_alg_release_parent);
 
 static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 {
-        const u32 forbidden = CRYPTO_ALG_INTERNAL;
+        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;
@@ -158,6 +158,10 @@ static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
         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;
 
@@ -176,9 +180,7 @@ static int alg_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
         if (IS_ERR(type))
                 return PTR_ERR(type);
 
-        private = type->bind(sa->salg_name,
-                             sa->salg_feat & ~forbidden,
-                             sa->salg_mask & ~forbidden);
+        private = type->bind(sa->salg_name, sa->salg_feat, sa->salg_mask);
         if (IS_ERR(private)) {
                 module_put(type->owner);
                 return PTR_ERR(private);