Subject: [RFC net-next 04/18] tuntap: check tun_msg_ctl type at necessary places

From: Prashant Bhole <[email-masked]>
Date: Tue, 26 Nov 2019 19:07:30 +0900

tun_msg_ctl is used by vhost_net to communicate with tuntap. We will
introduce another type in soon. As a preparation this patch adds
conditions to check tun_msg_ctl type at necessary places.

Signed-off-by: Prashant Bhole <[email-masked]>
---
 drivers/net/tap.c | 7 +++++--
 drivers/net/tun.c | 6 +++++-
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 3ae70c7e6860..4df7bf00af66 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1213,6 +1213,7 @@ static int tap_sendmsg(struct socket *sock, struct msghdr *m,
 	struct tap_queue *q = container_of(sock, struct tap_queue, sock);
 	struct tun_msg_ctl *ctl = m->msg_control;
 	struct xdp_buff *xdp;
+	void *ptr = NULL;
 	int i;
 
 	if (ctl && (ctl->type == TUN_MSG_PTR)) {
@@ -1223,8 +1224,10 @@ static int tap_sendmsg(struct socket *sock, struct msghdr *m,
 		return 0;
 	}
 
-	return tap_get_user(q, ctl ? ctl->ptr : NULL, &m->msg_iter,
-			    m->msg_flags & MSG_DONTWAIT);
+	if (ctl && ctl->type == TUN_MSG_UBUF)
+		ptr = ctl->ptr;
+
+	return tap_get_user(q, ptr, &m->msg_iter, m->msg_flags & MSG_DONTWAIT);
 }
 
 static int tap_recvmsg(struct socket *sock, struct msghdr *m,
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 683d371e6e82..1e436d9ec4e1 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2529,6 +2529,7 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 	struct tun_struct *tun = tun_get(tfile);
 	struct tun_msg_ctl *ctl = m->msg_control;
 	struct xdp_buff *xdp;
+	void *ptr = NULL;
 
 	if (!tun)
 		return -EBADFD;
@@ -2560,7 +2561,10 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 		goto out;
 	}
 
-	ret = tun_get_user(tun, tfile, ctl ? ctl->ptr : NULL, &m->msg_iter,
+	if (ctl && ctl->type == TUN_MSG_UBUF)
+		ptr = ctl->ptr;
+
+	ret = tun_get_user(tun, tfile, ptr, &m->msg_iter,
 			   m->msg_flags & MSG_DONTWAIT,
 			   m->msg_flags & MSG_MORE);
 out:
-- 
2.20.1