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From:   Harold Huang <baymaxhuang@gmail.com>
To:     netdev@vger.kernel.org
Cc:     jasowang@redhat.com, edumazet@google.com,
        Harold Huang <baymaxhuang@gmail.com>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        John Fastabend <john.fastabend@gmail.com>,
        linux-kernel@vger.kernel.org (open list),
        kvm@vger.kernel.org (open list:VIRTIO HOST (VHOST)),
        virtualization@lists.linux-foundation.org (open list:VIRTIO HOST
        (VHOST)), bpf@vger.kernel.org (open list:XDP (eXpress Data Path))
Subject: [PATCH net-next] tuntap: add sanity checks about msg_controllen in sendmsg
Date:   Tue,  1 Mar 2022 14:43:14 +0800
Message-Id: <20220301064314.2028737-1-baymaxhuang@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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