netdev - Re: [PATCH net] virtio-net: fix overflow inside virtnet_rq

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d3745969-df9b-47fa-8854-6654867f94e4@intel.com>
Date: Tue, 20 Aug 2024 17:12:31 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
CC: <netdev@...r.kernel.org>, "Michael S. Tsirkin" <mst@...hat.com>, "Jason
 Wang" <jasowang@...hat.com>, Eugenio Pérez
	<eperezma@...hat.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <virtualization@...ts.linux.dev>, Si-Wei Liu
	<si-wei.liu@...cle.com>, Darren Kenny <darren.kenny@...cle.com>
Subject: Re: [PATCH net] virtio-net: fix overflow inside virtnet_rq_alloc

From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Date: Tue, 20 Aug 2024 15:19:13 +0800

> leads to regression on VM with the sysctl value of:

Where's the beginning of the sentence? You mean, "This overflow leads"?

> 
> - net.core.high_order_alloc_disable=1

This `- ` can be removed - at least some syntax highlighters color it in
red :D

But I think you can just drop this reference to
high_order_alloc_disable. Just write that if the backing page is
order-0, then this happens.

> 
> which could see reliable crashes or scp failure (scp a file 100M in size
> to VM):
> 
> The issue is that the virtnet_rq_dma takes up 16 bytes at the beginning
> of a new frag. When the frag size is larger than PAGE_SIZE,
> everything is fine. However, if the frag is only one page and the
> total size of the buffer and virtnet_rq_dma is larger than one page, an
> overflow may occur. In this case, if an overflow is possible, I adjust
> the buffer size. If net.core.high_order_alloc_disable=1, the maximum
> buffer size is 4096 - 16. If net.core.high_order_alloc_disable=0, only
> the first buffer of the frag is affected.
> 
> Fixes: f9dac92ba908 ("virtio_ring: enable premapped mode whatever use_dma_api")
> Reported-by: "Si-Wei Liu" <si-wei.liu@...cle.com>
> Closes: http://lore.kernel.org/all/8b20cc28-45a9-4643-8e87-ba164a540c0a@oracle.com
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> ---
>  drivers/net/virtio_net.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index c6af18948092..e5286a6da863 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -918,9 +918,6 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
>  	void *buf, *head;
>  	dma_addr_t addr;
>  
> -	if (unlikely(!skb_page_frag_refill(size, alloc_frag, gfp)))
> -		return NULL;
> -
>  	head = page_address(alloc_frag->page);
>  
>  	dma = head;
> @@ -2421,6 +2418,9 @@ static int add_recvbuf_small(struct virtnet_info *vi, struct receive_queue *rq,
>  	len = SKB_DATA_ALIGN(len) +
>  	      SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
>  
> +	if (unlikely(!skb_page_frag_refill(len, &rq->alloc_frag, gfp)))
> +		return -ENOMEM;

Why did you move this call into the call sites?

> +
>  	buf = virtnet_rq_alloc(rq, len, gfp);
>  	if (unlikely(!buf))
>  		return -ENOMEM;
> @@ -2521,6 +2521,12 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi,
>  	 */
>  	len = get_mergeable_buf_len(rq, &rq->mrg_avg_pkt_len, room);
>  
> +	if (unlikely(!skb_page_frag_refill(len + room, alloc_frag, gfp)))
> +		return -ENOMEM;
> +
> +	if (!alloc_frag->offset && len + room + sizeof(struct virtnet_rq_dma) > alloc_frag->size)
> +		len -= sizeof(struct virtnet_rq_dma);
> +
>  	buf = virtnet_rq_alloc(rq, len + room, gfp);

`len + room` is referenced 3 times here, perhaps is worth a variable?

Is it fine that you decrease @len here?

>  	if (unlikely(!buf))
>  		return -ENOMEM;

Thanks,
Olek