在 2023/1/31 下午3:50, Michael S. Tsirkin 写道:
On Tue, Jan 31, 2023 at 03:40:32PM +0800, Heng Qi wrote:
On Tue, Jan 31, 2023 at 02:20:49AM -0500, Michael S. Tsirkin wrote:
On Tue, Jan 31, 2023 at 11:43:37AM +0800, Heng Qi wrote:
When the single-buffer xdp is loaded and after xdp_linearize_page()
is called, *num_buf becomes 0 and (*num_buf - 1) may overflow into
a large integer in virtnet_build_xdp_buff_mrg(), resulting in
unexpected packet dropping.
Fixes: ef75cb51f139 ("virtio-net: build xdp_buff with multi buffers")
Signed-off-by: Heng Qi <hengqi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Given the confusion, just make num_buf an int?
In the structure virtio_net_hdr_mrg_rxbuf, \field{num_buffers} is unsigned int,
which matches each other.
Because hardware buffers are all unsigned. Does not mean we need
to do all math unsigned now.
Yes.
And num_buf is used in many different places, it seems
to be a lot of work to modify it to int.
Are you sure?
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
I will also change to int in the next version.
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 18b3de854aeb..97f2e9bfc6f9 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -722,7 +722,7 @@ static unsigned int virtnet_get_headroom(struct virtnet_info *vi)
* have enough headroom.
*/
static struct page *xdp_linearize_page(struct receive_queue *rq,
- u16 *num_buf,
+ int *num_buf,
struct page *p,
int offset,
int page_off,
@@ -822,7 +822,7 @@ static struct sk_buff *receive_small(struct net_device *dev,
if (unlikely(xdp_headroom < virtnet_get_headroom(vi))) {
int offset = buf - page_address(page) + header_offset;
unsigned int tlen = len + vi->hdr_len;
- u16 num_buf = 1;
+ int num_buf = 1;
xdp_headroom = virtnet_get_headroom(vi);
header_offset = VIRTNET_RX_PAD + xdp_headroom;
@@ -948,7 +948,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
struct virtnet_rq_stats *stats)
{
struct virtio_net_hdr_mrg_rxbuf *hdr = buf;
- u16 num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
+ int num_buf = virtio16_to_cpu(vi->vdev, hdr->num_buffers);
struct page *page = virt_to_head_page(buf);
int offset = buf - page_address(page);
struct sk_buff *head_skb, *curr_skb;
Feel free to reuse.
---
drivers/net/virtio_net.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index aaa6fe9b214a..a8e9462903fa 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -1007,6 +1007,9 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
xdp_prepare_buff(xdp, buf - VIRTIO_XDP_HEADROOM,
VIRTIO_XDP_HEADROOM + vi->hdr_len, len - vi->hdr_len, true);
+ if (!*num_buf)
+ return 0;
+
if (*num_buf > 1) {
/* If we want to build multi-buffer xdp, we need
* to specify that the flags of xdp_buff have the
This means truesize won't be set.
Do you mean xdp_frags_truesize please? If yes, the answer is yes, this fix
is only for single-buffer xdp, which doesn't need xdp_frags_truesize, and
already set it to 0 in its wrapper receive_mergeable().
It seems cleaner to always set the value not rely on caller to do so.
Yes, I'll try to separate them in other patches.
Thanks.
@@ -1020,10 +1023,10 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
shinfo->xdp_frags_size = 0;
}
- if ((*num_buf - 1) > MAX_SKB_FRAGS)
+ if (*num_buf > MAX_SKB_FRAGS + 1)
return -EINVAL;
Admittedly this is cleaner.
- while ((--*num_buf) >= 1) {
+ while (--*num_buf) {
A bit more fragile, > 0 would be better.
Sure.
Thanks.
buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
if (unlikely(!buf)) {
pr_debug("%s: rx error: %d buffers out of %d missing\n",
--
2.19.1.6.gb485710b
