Re: [PATCH net] net: virtio_net: decode tunnel csum_start as little-endian

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] net: virtio_net: sparse __virtio16 mismatch in virtio_net_hdr_tnl_to_skb()
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commit ba7ce0ae4b2dfb77c6b110ada68faaf66de9237f
Author: Cheng Yongkang <teel4res@gmail.com>

net: virtio_net: decode tunnel csum_start as little-endian

This commit changes virtio_net_hdr_tnl_to_skb() in include/linux/virtio_net.h
to always decode hdr->csum_start as little-endian during tunnel header offset
validation, matching the subsequent call to __virtio_net_hdr_to_skb().

> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index d6466f96cdd00..ddc6341747e53 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -324,7 +324,7 @@ virtio_net_hdr_tnl_to_skb(struct sk_buff *skb,
>  	inner_l3min = virtio_l3min(inner_isv6);
>  	outer_l3min = ETH_HLEN + virtio_l3min(outer_isv6);
>  
> -	inner_th = __virtio16_to_cpu(little_endian, hdr->csum_start);
> +	inner_th = le16_to_cpu(hdr->csum_start);
>  	inner_nh = le16_to_cpu(vhdr->inner_nh_offset);
>  	outer_th = le16_to_cpu(vhdr->outer_th_offset);
>  	if (outer_th < outer_l3min ||

[Severity: Low]
Does passing hdr->csum_start directly to le16_to_cpu() in
virtio_net_hdr_tnl_to_skb() trigger sparse endianness warnings when building
callers such as drivers/net/virtio_net.c and drivers/net/tun.c with C=1?

Unlike vhdr->inner_nh_offset and vhdr->outer_th_offset, which are declared as
__le16 in struct virtio_net_hdr_v1_hash_tunnel, hdr->csum_start is declared as
__virtio16 in include/uapi/linux/virtio_net.h:

struct virtio_net_hdr {
	...
	__virtio16 csum_start;	/* Position to start checksumming from */
	__virtio16 csum_offset;	/* Offset after that to place checksum */
};

In include/linux/virtio_byteorder.h, __virtio16_to_cpu() performs the forced
cast from __virtio16 to __le16 before calling le16_to_cpu():

static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
{
	if (little_endian)
		return le16_to_cpu((__force __le16)val);
	else
		return be16_to_cpu((__force __be16)val);
}

Should this use __virtio16_to_cpu(true, hdr->csum_start) instead, matching the
__virtio_net_hdr_to_skb(skb, hdr, true, ...) call below and
__cpu_to_virtio16(true, hdr_len) in __virtio_net_set_tnl_hdrlen()?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/179268538303.70821.1734486381476363942@gmail.com?part=1