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

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Dec 26, 2023 at 10:01:13AM -0800, Stephen Hemminger wrote:
> 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

I would just use unsigned FWIW. But it doesn't matter the range is
limited here. It's just that the compiler can't figure it out.

-- 
MST