On Sat, Jul 17, 2021 at 06:20:30PM +0800, Xiyu Yang wrote:
> refcount_t type and corresponding API can protect refcounters from
> accidental underflow and overflow and further use-after-free situations.
>
> Signed-off-by: Xiyu Yang <xiyuyang19@xxxxxxxxxxxx>
> Signed-off-by: Xin Tan <tanxin.ctf@xxxxxxxxx>
Pls resubmit after addressing the build bot comments.
Thanks!
> ---
> drivers/vhost/net.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index 6414bd5741b8..e23150ca7d4c 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -5,6 +5,7 @@
> * virtio-net server in host kernel.
> */
>
> +#include <linux/refcount.h>
> #include <linux/compat.h>
> #include <linux/eventfd.h>
> #include <linux/vhost.h>
> @@ -92,7 +93,7 @@ struct vhost_net_ubuf_ref {
> * 1: no outstanding ubufs
> * >1: outstanding ubufs
> */
> - atomic_t refcount;
> + refcount_t refcount;
> wait_queue_head_t wait;
> struct vhost_virtqueue *vq;
> };
> @@ -240,7 +241,7 @@ vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)
> ubufs = kmalloc(sizeof(*ubufs), GFP_KERNEL);
> if (!ubufs)
> return ERR_PTR(-ENOMEM);
> - atomic_set(&ubufs->refcount, 1);
> + refcount_set(&ubufs->refcount, 1);
> init_waitqueue_head(&ubufs->wait);
> ubufs->vq = vq;
> return ubufs;
> @@ -248,7 +249,8 @@ vhost_net_ubuf_alloc(struct vhost_virtqueue *vq, bool zcopy)
>
> static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)
> {
> - int r = atomic_sub_return(1, &ubufs->refcount);
> + refcount_dec(&ubufs->refcount);
> + int r = refcount_read(&ubufs->refcount);
> if (unlikely(!r))
> wake_up(&ubufs->wait);
> return r;
> @@ -257,7 +259,7 @@ static int vhost_net_ubuf_put(struct vhost_net_ubuf_ref *ubufs)
> static void vhost_net_ubuf_put_and_wait(struct vhost_net_ubuf_ref *ubufs)
> {
> vhost_net_ubuf_put(ubufs);
> - wait_event(ubufs->wait, !atomic_read(&ubufs->refcount));
> + wait_event(ubufs->wait, !refcount_read(&ubufs->refcount));
> }
>
> static void vhost_net_ubuf_put_wait_and_free(struct vhost_net_ubuf_ref *ubufs)
> @@ -909,7 +911,7 @@ static void handle_tx_zerocopy(struct vhost_net *net, struct socket *sock)
> ctl.ptr = ubuf;
> msg.msg_controllen = sizeof(ctl);
> ubufs = nvq->ubufs;
> - atomic_inc(&ubufs->refcount);
> + refcount_inc(&ubufs->refcount);
> nvq->upend_idx = (nvq->upend_idx + 1) % UIO_MAXIOV;
> } else {
> msg.msg_control = NULL;
> @@ -1384,7 +1386,7 @@ static void vhost_net_flush(struct vhost_net *n)
> vhost_net_ubuf_put_and_wait(n->vqs[VHOST_NET_VQ_TX].ubufs);
> mutex_lock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
> n->tx_flush = false;
> - atomic_set(&n->vqs[VHOST_NET_VQ_TX].ubufs->refcount, 1);
> + refcount_set(&n->vqs[VHOST_NET_VQ_TX].ubufs->refcount, 1);
> mutex_unlock(&n->vqs[VHOST_NET_VQ_TX].vq.mutex);
> }
> }
> --
> 2.7.4
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