Re: [PATCH 1/1] virtio_net: Fix "‘%d’ directive writing between 1 and 11 bytes into a region of size 10" warnings

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 26 Dec 2023 19:53:58 +0800
Zhu Yanjun <yanjun.zhu@linux.dev> wrote:

> The warnings are as below:
> 
> "
> 
> drivers/net/virtio_net.c: In function ‘init_vqs’:
> drivers/net/virtio_net.c:4551:48: warning: ‘%d’ directive writing 
> between 1 and 11 bytes into a region of size 10 [-Wformat-overflow=]
>   4551 |                 sprintf(vi->rq[i].name, "input.%d", i);
>        |                                                ^~
> In function ‘virtnet_find_vqs’,
>      inlined from ‘init_vqs’ at drivers/net/virtio_net.c:4645:8:
> drivers/net/virtio_net.c:4551:41: note: directive argument in the range 
> [-2147483643, 65534]
>   4551 |                 sprintf(vi->rq[i].name, "input.%d", i);
>        |                                         ^~~~~~~~~~
> drivers/net/virtio_net.c:4551:17: note: ‘sprintf’ output between 8 and 
> 18 bytes into a destination of size 16
>   4551 |                 sprintf(vi->rq[i].name, "input.%d", i);
>        |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/net/virtio_net.c: In function ‘init_vqs’:
> drivers/net/virtio_net.c:4552:49: warning: ‘%d’ directive writing 
> between 1 and 11 bytes into a region of size 9 [-Wformat-overflow=]
>   4552 |                 sprintf(vi->sq[i].name, "output.%d", i);
>        |                                                 ^~
> In function ‘virtnet_find_vqs’,
>      inlined from ‘init_vqs’ at drivers/net/virtio_net.c:4645:8:
> drivers/net/virtio_net.c:4552:41: note: directive argument in the range 
> [-2147483643, 65534]
>   4552 |                 sprintf(vi->sq[i].name, "output.%d", i);
>        |                                         ^~~~~~~~~~~
> drivers/net/virtio_net.c:4552:17: note: ‘sprintf’ output between 9 and 
> 19 bytes into a destination of size 16
>   4552 |                 sprintf(vi->sq[i].name, "output.%d", i);
> 
> "
> 
> Please review.
> 
> Best Regards,
> 
> Zhu Yanjun
> 
> 在 2023/12/26 19:45, Zhu Yanjun 写道:
> > From: Zhu Yanjun <yanjun.zhu@linux.dev>
> >
> > Fix a warning when building virtio_net driver.
> >
> > Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
> > ---
> >   drivers/net/virtio_net.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 49625638ad43..cf57eddf768a 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -4508,10 +4508,11 @@ static int virtnet_find_vqs(struct virtnet_info *vi)
> >   {
> >   	vq_callback_t **callbacks;
> >   	struct virtqueue **vqs;
> > -	int ret = -ENOMEM;
> > -	int i, total_vqs;
> >   	const char **names;
> > +	int ret = -ENOMEM;
> > +	int total_vqs;
> >   	bool *ctx;
> > +	u16 i;
> >   
> >   	/* We expect 1 RX virtqueue followed by 1 TX virtqueue, followed by
> >   	 * possible N-1 RX/TX queue pairs used in multiqueue mode, followed by  
> 

If you change the variable type to u16, then the format string should no
longer use %d. Instead should be %u