Re: [PATCH] vhost_net: Convert from atomic_t to refcount_t on vhost_net_ubuf_ref->refcount
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From: Michael S. Tsirkin <mst@redhat.com>
Date: 2021-09-05 16:18:07
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kvm, lkml, virtualization
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 <redacted> Signed-off-by: Xin Tan <redacted>
Pls resubmit after addressing the build bot comments. Thanks!
quoted hunk ↗ jump to hunk
--- 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