Re: [PATCH net] xen-netfront: Add missing skb_mark_for_recycle

[Arthur Borsboom <arthurborsboom@xxxxxxxxx>]

On Wed, 27 Mar 2024 at 13:15, Jesper Dangaard Brouer <hawk@xxxxxxxxxx> wrote:
>
> Notice that skb_mark_for_recycle() is introduced later than fixes tag in
> 6a5bcd84e886 ("page_pool: Allow drivers to hint on SKB recycling").
>
> It is believed that fixes tag were missing a call to page_pool_release_page()
> between v5.9 to v5.14, after which is should have used skb_mark_for_recycle().
> Since v6.6 the call page_pool_release_page() were removed (in 535b9c61bdef
> ("net: page_pool: hide page_pool_release_page()") and remaining callers
> converted (in commit 6bfef2ec0172 ("Merge branch
> 'net-page_pool-remove-page_pool_release_page'")).
>
> This leak became visible in v6.8 via commit dba1b8a7ab68 ("mm/page_pool: catch
> page_pool memory leaks").
>
> Fixes: 6c5aa6fc4def ("xen networking: add basic XDP support for xen-netfront")
> Reported-by: Arthur Borsboom <arthurborsboom@xxxxxxxxx>
> Signed-off-by: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
> ---
> Compile tested only, can someone please test this

I have tested this patch on Xen 4.18.1 with VM (Arch Linux) kernel 6.9.0-rc1.

Without the patch there are many trace traces and cloning the Linux
mainline git repository resulted in failures (same with kernel 6.8.1).
The patched kernel 6.9.0-rc1 performs as expected; cloning the git
repository was successful and no kernel traces observed.
Hereby my tested by:

Tested-by: Arthur Borsboom <arthurborsboom@xxxxxxxxx>



>  drivers/net/xen-netfront.c |    1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index ad29f370034e..8d2aee88526c 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -285,6 +285,7 @@ static struct sk_buff *xennet_alloc_one_rx_buffer(struct 
> netfront_queue *queue)
>                 return NULL;
>         }
>         skb_add_rx_frag(skb, 0, page, 0, 0, PAGE_SIZE);
> +       skb_mark_for_recycle(skb);
>
>         /* Align ip header to a 16 bytes boundary */
>         skb_reserve(skb, NET_IP_ALIGN);
>
>