linux-kernel - Re: [PATCH] virtio_net: fix integer overflow in stats

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Message-ID: <riu6774ovfsubpe3zzuehfmzr2lz4slv6wmcsenoewl47nukf6@ba2tode64wby>
Date: Fri, 18 Oct 2024 16:39:41 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: linux-kernel@...r.kernel.org, 
	"Colin King (gmail)" <colin.i.king@...il.com>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez <eperezma@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, virtualization@...ts.linux.dev, 
	netdev@...r.kernel.org
Subject: Re: [PATCH] virtio_net: fix integer overflow in stats

On Wed, Oct 16, 2024 at 01:27:07PM -0400, Michael S. Tsirkin wrote:
>Static analysis on linux-next has detected the following issue
>in function virtnet_stats_ctx_init, in drivers/net/virtio_net.c :
>
>        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.
>
>In fact, the field is read into a u64:
>
>       u64 offset, bitmap;
>....
>       bitmap = ctx->bitmap[queue_type];
>
>so to fix, it is enough to make bitmap an array of u64.
>
>Fixes: 941168f8b40e5 ("virtio_net: support device stats")

Release with v6.10, so should we cc stable?

>Reported-by: "Colin King (gmail)" <colin.i.king@...il.com>
>Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>---
> drivers/net/virtio_net.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)

LGTM!

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

Thanks,
Stefano

>
>diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>index c6af18948092..b950d24b1ffa 100644
>--- a/drivers/net/virtio_net.c
>+++ b/drivers/net/virtio_net.c
>@@ -4112,7 +4112,7 @@ struct virtnet_stats_ctx {
> 	u32 desc_num[3];
>
> 	/* The actual supported stat types. */
>-	u32 bitmap[3];
>+	u64 bitmap[3];
>
> 	/* Used to calculate the reply buffer size. */
> 	u32 size[3];
>-- 
>MST
>
>