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Date: Thu, 2 Feb 2023 16:14:51 +0800
From: Heng Qi <hengqi@...ux.alibaba.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
Jason Wang <jasowang@...hat.com>,
Paolo Abeni <pabeni@...hat.com>,
Jakub Kicinski <kuba@...nel.org>,
John Fastabend <john.fastabend@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Subject: Re: [PATCH net-next v2] virtio-net: fix possible unsigned integer
overflow
在 2023/2/2 下午4:07, Michael S. Tsirkin 写道:
> On Tue, Jan 31, 2023 at 04:50:04PM +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@...ux.alibaba.com>
>> Reviewed-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
>> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>> ---
>> v1->v2:
>> - Change the type of num_buf from unsigned int to int. @Michael S . Tsirkin
>> - Some cleaner codes. @Michael S . Tsirkin
>>
>> drivers/net/virtio_net.c | 15 +++++++++------
>> 1 file changed, 9 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index aaa6fe9b214a..8102861785a2 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -716,7 +716,7 @@ 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,
>> @@ -816,7 +816,7 @@ 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;
>> @@ -989,7 +989,7 @@ static int virtnet_build_xdp_buff_mrg(struct net_device *dev,
>> void *buf,
>> unsigned int len,
>> unsigned int frame_sz,
>> - u16 *num_buf,
>> + int *num_buf,
>> unsigned int *xdp_frags_truesize,
>> struct virtnet_rq_stats *stats)
>> {
>> @@ -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
> Ouch. Why is this here? Merged so pls remove by a follow up patch, the
> rest of the code handles 0 fine. I'm not sure this introduces a bug by
> we don't want spaghetti code.
Yes it would work without this, but I was keeping this because I wanted
it to handle 0 early and exit early.
Do you want to remove this?
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;
>>
>> - while ((--*num_buf) >= 1) {
>> + while (--*num_buf > 0) {
>> buf = virtqueue_get_buf_ctx(rq->vq, &len, &ctx);
>> if (unlikely(!buf)) {
>> pr_debug("%s: rx error: %d buffers out of %d missing\n",
>> @@ -1076,7 +1079,7 @@ 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;
>> --
>> 2.19.1.6.gb485710b
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