From 6e474083f3daf3a3546737f5d7d502ad12eb257c Mon Sep 17 00:00:00 2001 From: Wei Xu Date: Fri, 1 Dec 2017 05:10:36 -0500 Subject: [PATCH 1/3] vhost: fix skb leak in handle_rx() Matthew found a roughly 40% tcp throughput regression with commit c67df11f(vhost_net: try batch dequing from skb array) as discussed in the following thread: https://www.mail-archive.com/netdev@vger.kernel.org/msg187936.html Eventually we figured out that it was a skb leak in handle_rx() when sending packets to the VM. This usually happens when a guest can not drain out vq as fast as vhost fills in, afterwards it sets off the traffic jam and leaks skb(s) which occurs as no headcount to send on the vq from vhost side. This can be avoided by making sure we have got enough headcount before actually consuming a skb from the batched rx array while transmitting, which is simply done by moving checking the zero headcount a bit ahead. Signed-off-by: Wei Xu Reported-by: Matthew Rosato Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/vhost/net.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 8d626d7c2e7e..c7bdeb655646 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -778,16 +778,6 @@ static void handle_rx(struct vhost_net *net) /* On error, stop handling until the next kick. */ if (unlikely(headcount < 0)) goto out; - if (nvq->rx_array) - msg.msg_control = vhost_net_buf_consume(&nvq->rxq); - /* On overrun, truncate and discard */ - if (unlikely(headcount > UIO_MAXIOV)) { - iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1); - err = sock->ops->recvmsg(sock, &msg, - 1, MSG_DONTWAIT | MSG_TRUNC); - pr_debug("Discarded rx packet: len %zd\n", sock_len); - continue; - } /* OK, now we need to know about added descriptors. */ if (!headcount) { if (unlikely(vhost_enable_notify(&net->dev, vq))) { @@ -800,6 +790,16 @@ static void handle_rx(struct vhost_net *net) * they refilled. */ goto out; } + if (nvq->rx_array) + msg.msg_control = vhost_net_buf_consume(&nvq->rxq); + /* On overrun, truncate and discard */ + if (unlikely(headcount > UIO_MAXIOV)) { + iov_iter_init(&msg.msg_iter, READ, vq->iov, 1, 1); + err = sock->ops->recvmsg(sock, &msg, + 1, MSG_DONTWAIT | MSG_TRUNC); + pr_debug("Discarded rx packet: len %zd\n", sock_len); + continue; + } /* We don't need to be notified again. */ iov_iter_init(&msg.msg_iter, READ, vq->iov, in, vhost_len); fixup = msg.msg_iter; From c33ee15b3820a03cf8229ba9415084197b827f8c Mon Sep 17 00:00:00 2001 From: Wei Xu Date: Fri, 1 Dec 2017 05:10:37 -0500 Subject: [PATCH 2/3] tun: free skb in early errors tun_recvmsg() supports accepting skb by msg_control after commit ac77cfd4258f ("tun: support receiving skb through msg_control"), the skb if presented should be freed no matter how far it can go along, otherwise it would be leaked. This patch fixes several missed cases. Signed-off-by: Wei Xu Reported-by: Matthew Rosato Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- drivers/net/tun.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 95749006d687..4f4a842a1c9c 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1952,8 +1952,11 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile, tun_debug(KERN_INFO, tun, "tun_do_read\n"); - if (!iov_iter_count(to)) + if (!iov_iter_count(to)) { + if (skb) + kfree_skb(skb); return 0; + } if (!skb) { /* Read frames from ring */ @@ -2069,22 +2072,24 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len, { struct tun_file *tfile = container_of(sock, struct tun_file, socket); struct tun_struct *tun = tun_get(tfile); + struct sk_buff *skb = m->msg_control; int ret; - if (!tun) - return -EBADFD; + if (!tun) { + ret = -EBADFD; + goto out_free_skb; + } if (flags & ~(MSG_DONTWAIT|MSG_TRUNC|MSG_ERRQUEUE)) { ret = -EINVAL; - goto out; + goto out_put_tun; } if (flags & MSG_ERRQUEUE) { ret = sock_recv_errqueue(sock->sk, m, total_len, SOL_PACKET, TUN_TX_TIMESTAMP); goto out; } - ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT, - m->msg_control); + ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT, skb); if (ret > (ssize_t)total_len) { m->msg_flags |= MSG_TRUNC; ret = flags & MSG_TRUNC ? ret : total_len; @@ -2092,6 +2097,13 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len, out: tun_put(tun); return ret; + +out_put_tun: + tun_put(tun); +out_free_skb: + if (skb) + kfree_skb(skb); + return ret; } static int tun_peek_len(struct socket *sock) From 61d78537843e676e7f56ac6db333db0c0529b892 Mon Sep 17 00:00:00 2001 From: Wei Xu Date: Fri, 1 Dec 2017 05:10:38 -0500 Subject: [PATCH 3/3] tap: free skb if flags error 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 Reported-by: Matthew Rosato Acked-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- 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 e9489b88407c..0a886fda0129 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;