[PATCH net-next] tuntap: add sanity checks about msg_controllen in sendmsg

Harold Huang
2022-03-03T02:25:16Z

In patch [1], tun_msg_ctl was added to allow pass batched xdp buffers to
tun_sendmsg. Although we donot use msg_controllen in this path, we should
check msg_controllen to make sure the caller pass a valid msg_ctl.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fe8dd45bb7556246c6b76277b1ba4296c91c2505

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Harold Huang <baymaxhuang@gmail.com>
---
drivers/net/tap.c | 3 ++-
drivers/net/tun.c | 3 ++-
drivers/vhost/net.c | 1 +
3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index 8e3a28ba6b28..ba2ef5437e16 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1198,7 +1198,8 @@ static int tap_sendmsg(struct socket *sock, struct msghdr *m,
struct xdp_buff *xdp;
int i;

- if (ctl && (ctl->type == TUN_MSG_PTR)) {
+ if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
+ ctl && ctl->type == TUN_MSG_PTR) {
for (i = 0; i < ctl->num; i++) {
xdp = &((struct xdp_buff *)ctl->ptr)[i];
tap_get_user_xdp(q, xdp);
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 969ea69fd29d..2a0d8a5d7aec 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2501,7 +2501,8 @@ static int tun_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
if (!tun)
return -EBADFD;

- if (ctl && (ctl->type == TUN_MSG_PTR)) {
+ if (m->msg_controllen == sizeof(struct tun_msg_ctl) &&
+ ctl && ctl->type == TUN_MSG_PTR) {
struct tun_page tpage;
int n = ctl->num;
int flush = 0, queued = 0;
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 28ef323882fb..792ab5f23647 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -473,6 +473,7 @@ static void vhost_tx_batch(struct vhost_net *net,
goto signal_used;

msghdr->msg_control = &ctl;
+ msghdr->msg_controllen = sizeof(ctl);
err = sock->ops->sendmsg(sock, msghdr, 0);
if (unlikely(err < 0)) {
vq_err(&nvq->vq, "Fail to batch sending packets\n");
--
2.27.0