Re: [PATCH] vt: keyboard, fix uninitialized variables warning

[Wang, Li]

On 3/3/2021 3:14 PM, Greg KH wrote:
> On Wed, Mar 03, 2021 at 12:59:32PM +0800, Li Wang wrote:
> > drivers/tty/vt/keyboard.c: In function 'vt_do_kdgkb_ioctl':
> > drivers/tty/vt/keyboard.c: warning: 'ret' may be used uninitialized in this function [-Wmaybe-uninitialized]
> >    return ret;
> >           ^~~
> > kernel-source/drivers/tty/vt/keyboard.c: warning: 'kbs' may be used uninitialized in this function [-Wmaybe-uninitialized]
> >    kfree(kbs);
> >    ^~~~~~~~~~
> >
> > Signed-off-by: Li Wang <li.wang@xxxxxxxxxxxxx>
> > ---
> >   drivers/tty/vt/keyboard.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/tty/vt/keyboard.c b/drivers/tty/vt/keyboard.c
> > index 7763862..3e73d55 100644
> > --- a/drivers/tty/vt/keyboard.c
> > +++ b/drivers/tty/vt/keyboard.c
> > @@ -2049,8 +2049,8 @@ int vt_do_kdgkb_ioctl(int cmd, struct kbsentry __user *user_kdgkb, int perm)
> >   {
> >   	unsigned char kb_func;
> >   	unsigned long flags;
> > -	char *kbs;
> > -	int ret;
> > +	char *kbs = NULL;
> > +	int ret = -EINVAL;
> >   
> >   	if (get_user(kb_func, &user_kdgkb->kb_func))
> >   		return -EFAULT;
> What compiler is providing these "warnings"?
>
> Turns out it is impossible to hit, so this isn't actually fixing
> anything...

I tested it with gcc 8.2 for arm

for runtime codes view, indeed it is impossible to hit.

but for compiler view, gcc should give 'used uninitialized' warning, too.

thank for your reply,
LiWang.

> thanks,
>
> greg k-h