re: virtio_net: support device stats

[Colin King (gmail)]

Hi,

Static analysis on Linux-next has detected a potential issue with the 
following commit:

commit 941168f8b40e50518a3bc6ce770a7062a5d99230
Author: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Date:   Fri Apr 26 11:39:24 2024 +0800

    virtio_net: support device stats


The issue is in function virtnet_stats_ctx_init, in 
drivers/net/virtio_net.c as follows:

        if (vi->device_stats_cap & VIRTIO_NET_STATS_TYPE_CVQ) {
                queue_type = VIRTNET_Q_TYPE_CQ;

                ctx->bitmap[queue_type]   |= VIRTIO_NET_STATS_TYPE_CVQ;
                ctx->desc_num[queue_type] += 
ARRAY_SIZE(virtnet_stats_cvq_desc);
                ctx->size[queue_type]     += sizeof(struct 
virtio_net_stats_cvq);
        }


ctx->bitmap is declared as a u32 however it is being bit-wise or'd with 
VIRTIO_NET_STATS_TYPE_CVQ and this is defined as 1 << 32:

include/uapi/linux/virtio_net.h:#define VIRTIO_NET_STATS_TYPE_CVQ 
(1ULL << 32)

..and hence the bit-wise or operation won't set any bits in ctx->bitmap 
because 1ULL < 32 is too wide for a u32. I suspect ctx->bitmap should be 
declared as u64.

Colin