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Subject[PATCH net 3/9] virtio-net: fix page miscount during XDP linearizing
Date
We don't put page during linearizing, the would cause leaking when
xmit through XDP_TX or the packet exceeds PAGE_SIZE. Fix them by
put page accordingly. Also decrease the number of buffers during
linearizing to make sure caller can free buffers correctly when packet
exceeds PAGE_SIZE. With this patch, we won't get OOM after linearize
huge number of packets.

Cc: John Fastabend <john.r.fastabend@intel.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/virtio_net.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fe4562d..58ad40e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -483,7 +483,7 @@ static struct sk_buff *receive_big(struct net_device *dev,
* anymore.
*/
static struct page *xdp_linearize_page(struct receive_queue *rq,
- u16 num_buf,
+ u16 *num_buf,
struct page *p,
int offset,
unsigned int *len)
@@ -497,7 +497,7 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
memcpy(page_address(page) + page_off, page_address(p) + offset, *len);
page_off += *len;

- while (--num_buf) {
+ while (--*num_buf) {
unsigned int buflen;
unsigned long ctx;
void *buf;
@@ -507,19 +507,22 @@ static struct page *xdp_linearize_page(struct receive_queue *rq,
if (unlikely(!ctx))
goto err_buf;

+ buf = mergeable_ctx_to_buf_address(ctx);
+ p = virt_to_head_page(buf);
+ off = buf - page_address(p);
+
/* guard against a misconfigured or uncooperative backend that
* is sending packet larger than the MTU.
*/
- if ((page_off + buflen) > PAGE_SIZE)
+ if ((page_off + buflen) > PAGE_SIZE) {
+ put_page(p);
goto err_buf;
-
- buf = mergeable_ctx_to_buf_address(ctx);
- p = virt_to_head_page(buf);
- off = buf - page_address(p);
+ }

memcpy(page_address(page) + page_off,
page_address(p) + off, buflen);
page_off += buflen;
+ put_page(p);
}

*len = page_off;
@@ -555,7 +558,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
/* This happens when rx buffer size is underestimated */
if (unlikely(num_buf > 1)) {
/* linearize data for XDP */
- xdp_page = xdp_linearize_page(rq, num_buf,
+ xdp_page = xdp_linearize_page(rq, &num_buf,
page, offset, &len);
if (!xdp_page)
goto err_xdp;
--
2.7.4
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