netdev - Re: [PATCH v15 bpf-next 17/18] net: xdp: introduce bpf_xdp

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Date:   Fri, 8 Oct 2021 18:10:26 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org,
        lorenzo.bianconi@...hat.com, davem@...emloft.net, ast@...nel.org,
        daniel@...earbox.net, shayagr@...zon.com, john.fastabend@...il.com,
        dsahern@...nel.org, brouer@...hat.com, echaudro@...hat.com,
        jasowang@...hat.com, alexander.duyck@...il.com, saeed@...nel.org,
        maciej.fijalkowski@...el.com, magnus.karlsson@...el.com,
        tirthendu.sarkar@...el.com, toke@...hat.com
Subject: Re: [PATCH v15 bpf-next 17/18] net: xdp: introduce bpf_xdp_pointer
 utility routine

On Fri,  8 Oct 2021 14:49:55 +0200 Lorenzo Bianconi wrote:
> +BPF_CALL_4(bpf_xdp_load_bytes, struct xdp_buff *, xdp, u32, offset,
> +	   void *, buf, u32, len)
> +{
> +	void *ptr;
> +
> +	if (!buf)
> +		return -EINVAL;

Can we make the verifier ensure it's not NULL?

> +	ptr = bpf_xdp_pointer(xdp, offset, len, buf);
> +	if (ptr != buf)
> +		memcpy(buf, ptr, len);

Don't we need to return an error in case offset + length > frame size?

> +	return 0;
> +}