On Fri, Feb 02, 2024 at 05:32:20PM +0100, Sebastian Andrzej Siewior wrote:
> xsk_build_skb() allocates a page and adds it to the skb via
> skb_add_rx_frag() and specifies 0 for truesize. This leads to a warning
> in skb_add_rx_frag() with CONFIG_DEBUG_NET enabled because size is
> larger than truesize.
>
> Increasing truesize requires to add the same amount to socket's
> sk_wmem_alloc counter in order not to underflow the counter during
> release in the destructor (sock_wfree()).
>
> Pass the size of the allocated page as truesize to skb_add_rx_frag().
> Add this mount to socket's sk_wmem_alloc counter.
>
> Fixes: cf24f5a5feea ("xsk: add support for AF_XDP multi-buffer on Tx path")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Thanks a lot! Of course fix is totally correct.
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx>
> ---
> Noticed by running test_xsk.sh
>
> net/xdp/xsk.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 0348e4bde23b2..3050739cfe1e0 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -744,7 +744,8 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
> memcpy(vaddr, buffer, len);
> kunmap_local(vaddr);
>
> - skb_add_rx_frag(skb, nr_frags, page, 0, len, 0);
> + skb_add_rx_frag(skb, nr_frags, page, 0, len, PAGE_SIZE);
> + refcount_add(PAGE_SIZE, &xs->sk.sk_wmem_alloc);
> }
>
> if (first_frag && desc->options & XDP_TX_METADATA) {
> --
> 2.43.0
>
