Subject: [PATCH 25/33] tap: free skb if flags error

From: Wei Xu <[email-masked]>
Date: Fri, 1 Dec 2017 05:10:38 -0500

[ Upstream commit 61d78537843e676e7f56ac6db333db0c0529b892 ]

tap_recvmsg() supports accepting skb by msg_control after
commit 3b4ba04acca8 ("tap: support receiving skb from msg_control"),
the skb if presented should be freed within the function, otherwise
it would be leaked.

Signed-off-by: Wei Xu <[email-masked]>
Reported-by: Matthew Rosato <[email-masked]>
Acked-by: Michael S. Tsirkin <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 drivers/net/tap.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 6c0c84c33e1f..e4c6c78fab3b 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -829,8 +829,11 @@ static ssize_t tap_do_read(struct tap_queue *q,
 	DEFINE_WAIT(wait);
 	ssize_t ret = 0;
 
-	if (!iov_iter_count(to))
+	if (!iov_iter_count(to)) {
+		if (skb)
+			kfree_skb(skb);
 		return 0;
+	}
 
 	if (skb)
 		goto put;
@@ -1154,11 +1157,14 @@ static int tap_recvmsg(struct socket *sock, struct msghdr *m,
 		       size_t total_len, int flags)
 {
 	struct tap_queue *q = container_of(sock, struct tap_queue, sock);
+	struct sk_buff *skb = m->msg_control;
 	int ret;
-	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
+	if (flags & ~(MSG_DONTWAIT|MSG_TRUNC)) {
+		if (skb)
+			kfree_skb(skb);
 		return -EINVAL;
-	ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT,
-			  m->msg_control);
+	}
+	ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT, skb);
 	if (ret > total_len) {
 		m->msg_flags |= MSG_TRUNC;
 		ret = flags & MSG_TRUNC ? ret : total_len;
-- 
2.14.3