Subject: Re: [PATCH 1/1] ionic: fix array overflow on receiving too many fragments for a packet

From: Jesse Brandeburg <[email-masked]>
Date: Sun, 6 Dec 2020 17:51:57 -0800

Xiaohui Zhang wrote:

> From: Zhang Xiaohui <[email-masked]>
> 
> If the hardware receives an oversized packet with too many rx fragments,
> skb_shinfo(skb)->frags can overflow and corrupt memory of adjacent pages.
> This becomes especially visible if it corrupts the freelist pointer of
> a slab page.
> 
> Signed-off-by: Zhang Xiaohui <[email-masked]>

Hi, thanks for your patch.

It appears this is a part of a series of patches (at least this one and
one to the ice driver) - please send as one series, with a cover letter
explanation.

Please justify how this is a bug and how this is found / reproduced.

I'll respond separately to the ice driver patch as I don't know this
hardware and it's limits, but I suspect that you've tried to fix a bug
where there was none. (It seems like something a code scanner might find
and be confused about)

> ---
>  drivers/net/ethernet/pensando/ionic/ionic_txrx.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> index 169ac4f54..a3e274c65 100644
> --- a/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> +++ b/drivers/net/ethernet/pensando/ionic/ionic_txrx.c
> @@ -102,8 +102,12 @@ static struct sk_buff *ionic_rx_frags(struct ionic_queue *q,
>  
>  		dma_unmap_page(dev, dma_unmap_addr(page_info, dma_addr),
>  			       PAGE_SIZE, DMA_FROM_DEVICE);
> -		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
> +		struct skb_shared_info *shinfo = skb_shinfo(skb);

you can't declare variables in the middle of a code flow in C, did you
compile this?

> +
> +		if (shinfo->nr_frags < ARRAY_SIZE(shinfo->frags)) {
> +			skb_add_rx_frag(skb, shinfo->nr_frags,
>  				page_info->page, 0, frag_len, PAGE_SIZE);
> +		}
>  		page_info->page = NULL;
>  		page_info++;
>  		i--;