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-rw-r--r--net/9p/trans_virtio.c23
1 files changed, 22 insertions, 1 deletions
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index c6e1ae2fb926..e8f046b07182 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -43,6 +43,7 @@
#include <net/9p/client.h>
#include <net/9p/transport.h>
#include <linux/scatterlist.h>
+#include <linux/swap.h>
#include <linux/virtio.h>
#include <linux/virtio_9p.h>
#include "trans_common.h"
@@ -51,6 +52,8 @@
/* a single mutex to manage channel initialization and attachment */
static DEFINE_MUTEX(virtio_9p_lock);
+static DECLARE_WAIT_QUEUE_HEAD(vp_wq);
+static atomic_t vp_pinned = ATOMIC_INIT(0);
/**
* struct virtio_chan - per-instance transport information
@@ -78,7 +81,10 @@ struct virtio_chan {
struct virtqueue *vq;
int ring_bufs_avail;
wait_queue_head_t *vc_wq;
-
+ /* This is global limit. Since we don't have a global structure,
+ * will be placing it in each channel.
+ */
+ int p9_max_pages;
/* Scatterlist: can be too big for stack. */
struct scatterlist sg[VIRTQUEUE_NUM];
@@ -159,8 +165,11 @@ static void req_done(struct virtqueue *vq)
req = p9_tag_lookup(chan->client, rc->tag);
if (req->tc->private) {
struct trans_rpage_info *rp = req->tc->private;
+ int p = rp->rp_nr_pages;
/*Release pages */
p9_release_req_pages(rp);
+ atomic_sub(p, &vp_pinned);
+ wake_up(&vp_wq);
if (rp->rp_alloc)
kfree(rp);
req->tc->private = NULL;
@@ -269,6 +278,14 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
int rpinfo_size = sizeof(struct trans_rpage_info) +
sizeof(struct page *) * nr_pages;
+ if (atomic_read(&vp_pinned) >= chan->p9_max_pages) {
+ err = wait_event_interruptible(vp_wq,
+ atomic_read(&vp_pinned) < chan->p9_max_pages);
+ if (err == -ERESTARTSYS)
+ return err;
+ P9_DPRINTK(P9_DEBUG_TRANS, "9p: May gup pages now.\n");
+ }
+
if (rpinfo_size <= (req->tc->capacity - req->tc->size)) {
/* We can use sdata */
req->tc->private = req->tc->sdata + req->tc->size;
@@ -291,6 +308,8 @@ p9_virtio_request(struct p9_client *client, struct p9_req_t *req)
if (rpinfo->rp_alloc)
kfree(rpinfo);
return err;
+ } else {
+ atomic_add(rpinfo->rp_nr_pages, &vp_pinned);
}
}
@@ -452,6 +471,8 @@ static int p9_virtio_probe(struct virtio_device *vdev)
}
init_waitqueue_head(chan->vc_wq);
chan->ring_bufs_avail = 1;
+ /* Ceiling limit to avoid denial of service attacks */
+ chan->p9_max_pages = nr_free_buffer_pages()/4;
mutex_lock(&virtio_9p_lock);
list_add_tail(&chan->chan_list, &virtio_chan_list);