diff mbox series

[net,v5,1/2] vhost_net: fix ubuf refcount incorrectly when sendmsg fails

Message ID 1608881065-7572-1-git-send-email-wangyunjian@huawei.com
State New
Headers show
Series [net,v5,1/2] vhost_net: fix ubuf refcount incorrectly when sendmsg fails | expand

Commit Message

wangyunjian Dec. 25, 2020, 7:24 a.m. UTC 
From: Yunjian Wang <wangyunjian@huawei.com>

Currently the vhost_zerocopy_callback() maybe be called to decrease
the refcount when sendmsg fails in tun. The error handling in vhost
handle_tx_zerocopy() will try to decrease the same refcount again.
This is wrong. To fix this issue, we only call vhost_net_ubuf_put()
when vq->heads[nvq->desc].len == VHOST_DMA_IN_PROGRESS.

Fixes: 0690899b4d45 ("tun: experimental zero copy tx support")
Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vhost/net.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Comments

Michael S. Tsirkin Dec. 27, 2020, 11:23 a.m. UTC | #1 
On Fri, Dec 25, 2020 at 03:24:25PM +0800, wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@huawei.com>

> 

> Currently the vhost_zerocopy_callback() maybe be called to decrease

> the refcount when sendmsg fails in tun. The error handling in vhost

> handle_tx_zerocopy() will try to decrease the same refcount again.

> This is wrong. To fix this issue, we only call vhost_net_ubuf_put()

> when vq->heads[nvq->desc].len == VHOST_DMA_IN_PROGRESS.

> 

> Fixes: 0690899b4d45 ("tun: experimental zero copy tx support")


Are you sure about this tag? the patch in question only affects
tun, while the fix only affects vhost.

> Signed-off-by: Yunjian Wang <wangyunjian@huawei.com>

> Acked-by: Willem de Bruijn <willemb@google.com>

> Acked-by: Michael S. Tsirkin <mst@redhat.com>

> Acked-by: Jason Wang <jasowang@redhat.com>

> ---

>  drivers/vhost/net.c | 6 +++---

>  1 file changed, 3 insertions(+), 3 deletions(-)

> 

> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c

> index 531a00d703cd..c8784dfafdd7 100644

> --- a/drivers/vhost/net.c

> +++ b/drivers/vhost/net.c

> @@ -863,6 +863,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)

>  	size_t len, total_len = 0;

>  	int err;

>  	struct vhost_net_ubuf_ref *ubufs;

> +	struct ubuf_info *ubuf;

>  	bool zcopy_used;

>  	int sent_pkts = 0;

>  

> @@ -895,9 +896,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)

>  

>  		/* use msg_control to pass vhost zerocopy ubuf info to skb */

>  		if (zcopy_used) {

> -			struct ubuf_info *ubuf;

>  			ubuf = nvq->ubuf_info + nvq->upend_idx;

> -

>  			vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);

>  			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;

>  			ubuf->callback = vhost_zerocopy_callback;

> @@ -927,7 +926,8 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)

>  		err = sock->ops->sendmsg(sock, &msg, len);

>  		if (unlikely(err < 0)) {

>  			if (zcopy_used) {

> -				vhost_net_ubuf_put(ubufs);

> +				if (vq->heads[ubuf->desc].len == VHOST_DMA_IN_PROGRESS)

> +					vhost_net_ubuf_put(ubufs);

>  				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)

>  					% UIO_MAXIOV;

>  			}

> -- 

> 2.23.0
Willem de Bruijn Dec. 27, 2020, 4:14 p.m. UTC | #2 
On Sun, Dec 27, 2020 at 6:26 AM Michael S. Tsirkin <mst@redhat.com> wrote:
>

> On Fri, Dec 25, 2020 at 03:24:25PM +0800, wangyunjian wrote:

> > From: Yunjian Wang <wangyunjian@huawei.com>

> >

> > Currently the vhost_zerocopy_callback() maybe be called to decrease

> > the refcount when sendmsg fails in tun. The error handling in vhost

> > handle_tx_zerocopy() will try to decrease the same refcount again.

> > This is wrong. To fix this issue, we only call vhost_net_ubuf_put()

> > when vq->heads[nvq->desc].len == VHOST_DMA_IN_PROGRESS.

> >

> > Fixes: 0690899b4d45 ("tun: experimental zero copy tx support")

>

> Are you sure about this tag? the patch in question only affects

> tun, while the fix only affects vhost.


That was my suggestion. But you're right. Perhaps better:

Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support")

That introduces the actual block that releases the buffer on error:

"
                err = sock->ops->sendmsg(NULL, sock, &msg, len);
                if (unlikely(err < 0)) {
+                       if (zcopy) {
+                               if (ubufs)
+                                       vhost_ubuf_put(ubufs);
+                               vq->upend_idx = ((unsigned)vq->upend_idx - 1) %
+                                       UIO_MAXIOV;
+                       }
"
wangyunjian Dec. 28, 2020, 11:58 a.m. UTC | #3 
> -----Original Message-----

> From: Willem de Bruijn [mailto:willemdebruijn.kernel@gmail.com]

> Sent: Monday, December 28, 2020 12:15 AM

> To: Michael S. Tsirkin <mst@redhat.com>

> Cc: wangyunjian <wangyunjian@huawei.com>; Network Development

> <netdev@vger.kernel.org>; Jason Wang <jasowang@redhat.com>; Willem de

> Bruijn <willemdebruijn.kernel@gmail.com>;

> virtualization@lists.linux-foundation.org; Lilijun (Jerry)

> <jerry.lilijun@huawei.com>; chenchanghu <chenchanghu@huawei.com>;

> xudingke <xudingke@huawei.com>; huangbin (J)

> <brian.huangbin@huawei.com>

> Subject: Re: [PATCH net v5 1/2] vhost_net: fix ubuf refcount incorrectly when

> sendmsg fails

> 

> On Sun, Dec 27, 2020 at 6:26 AM Michael S. Tsirkin <mst@redhat.com> wrote:

> >

> > On Fri, Dec 25, 2020 at 03:24:25PM +0800, wangyunjian wrote:

> > > From: Yunjian Wang <wangyunjian@huawei.com>

> > >

> > > Currently the vhost_zerocopy_callback() maybe be called to decrease

> > > the refcount when sendmsg fails in tun. The error handling in vhost

> > > handle_tx_zerocopy() will try to decrease the same refcount again.

> > > This is wrong. To fix this issue, we only call vhost_net_ubuf_put()

> > > when vq->heads[nvq->desc].len == VHOST_DMA_IN_PROGRESS.

> > >

> > > Fixes: 0690899b4d45 ("tun: experimental zero copy tx support")

> >

> > Are you sure about this tag? the patch in question only affects tun,

> > while the fix only affects vhost.

> 

> That was my suggestion. But you're right. Perhaps better:

> 

> Fixes: bab632d69ee4 ("vhost: vhost TX zero-copy support")


OK, thanks, I will fix it in next version.

> 

> That introduces the actual block that releases the buffer on error:

> 

> "

>                 err = sock->ops->sendmsg(NULL, sock, &msg, len);

>                 if (unlikely(err < 0)) {

> +                       if (zcopy) {

> +                               if (ubufs)

> +                                       vhost_ubuf_put(ubufs);

> +                               vq->upend_idx =

> ((unsigned)vq->upend_idx - 1) %

> +                                       UIO_MAXIOV;

> +                       }

> "
diff mbox series

Patch

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 531a00d703cd..c8784dfafdd7 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -863,6 +863,7 @@  static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
 	size_t len, total_len = 0;
 	int err;
 	struct vhost_net_ubuf_ref *ubufs;
+	struct ubuf_info *ubuf;
 	bool zcopy_used;
 	int sent_pkts = 0;
 
@@ -895,9 +896,7 @@  static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
 
 		/* use msg_control to pass vhost zerocopy ubuf info to skb */
 		if (zcopy_used) {
-			struct ubuf_info *ubuf;
 			ubuf = nvq->ubuf_info + nvq->upend_idx;
-
 			vq->heads[nvq->upend_idx].id = cpu_to_vhost32(vq, head);
 			vq->heads[nvq->upend_idx].len = VHOST_DMA_IN_PROGRESS;
 			ubuf->callback = vhost_zerocopy_callback;
@@ -927,7 +926,8 @@  static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
 		err = sock->ops->sendmsg(sock, &msg, len);
 		if (unlikely(err < 0)) {
 			if (zcopy_used) {
-				vhost_net_ubuf_put(ubufs);
+				if (vq->heads[ubuf->desc].len == VHOST_DMA_IN_PROGRESS)
+					vhost_net_ubuf_put(ubufs);
 				nvq->upend_idx = ((unsigned)nvq->upend_idx - 1)
 					% UIO_MAXIOV;
 			}