[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date: Thu, 2 Feb 2023 18:55:34 +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6:31, Michael S. Tsirkin 写道:
> On Thu, Feb 02, 2023 at 05:07:04PM +0800, Heng Qi wrote:
>>
>> 在 2023/2/2 下午4:16, Michael S. Tsirkin 写道:
>>> On Thu, Feb 02, 2023 at 04:14:51PM +0800, Heng Qi wrote:
>>>> 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.
>>> why do you want to exit early?
>> If num_buf is 0, we don't need to judge the subsequent process, because the
>> latter process
>> is used to build multi-buffer xdp, but this fix solves the possible problems
>> of single-buffer xdp.
>>
>> Thanks.
> An optimization then? As any optimization I'd like to see some numbers.
>
> Should have been documented as such not as part of a bugfix.
Sure, I'm going to remove this with a follow-up patch.😁
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
Powered by blists - more mailing lists