linux-kernel - Re: [PATCH][next] lkdtm: remove redundant initialization of ret

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Message-ID: <201906210920.E133B26C@keescook>
Date:   Fri, 21 Jun 2019 09:26:05 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Colin King <colin.king@...onical.com>,
        Arnd Bergmann <arnd@...db.de>, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] lkdtm: remove redundant initialization of ret

On Fri, Jun 21, 2019 at 04:05:09PM +0200, Greg Kroah-Hartman wrote:
> On Fri, Jun 21, 2019 at 04:03:47PM +0200, Greg Kroah-Hartman wrote:
> > On Fri, Jun 14, 2019 at 10:43:11AM +0100, Colin King wrote:
> > > From: Colin Ian King <colin.king@...onical.com>
> > > 
> > > The variable ret is being initialized with the value -EINVAL however
> > > this value is never read and ret is being re-assigned later on. Hence
> > > the initialization is redundant and can be removed.
> > > 
> > > Addresses-Coverity: ("Unused value")
> > > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > > Acked-by: Kees Cook <keescook@...omium.org>
> > > ---
> > >  drivers/misc/lkdtm/core.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/misc/lkdtm/core.c b/drivers/misc/lkdtm/core.c
> > > index bba093224813..92df35fdeab0 100644
> > > --- a/drivers/misc/lkdtm/core.c
> > > +++ b/drivers/misc/lkdtm/core.c
> > > @@ -390,7 +390,7 @@ static int __init lkdtm_module_init(void)
> > >  {
> > >  	struct crashpoint *crashpoint = NULL;
> > >  	const struct crashtype *crashtype = NULL;
> > > -	int ret = -EINVAL;
> > > +	int ret;
> > >  	int i;
> > >  
> > >  	/* Neither or both of these need to be set */
> > > -- 
> > > 2.20.1
> > > 
> > 
> > With this patch now applied, I get this build warning:
> > drivers/misc/lkdtm/core.c: In function lkdtm_module_init:
> > drivers/misc/lkdtm/core.c:467:9: warning: ret may be used uninitialized in this function [-Wmaybe-uninitialized]
> >   return ret;
> >          ^~~
> > 
> > So are you _sure_ it shouldn't be initialized?
> 
> In looking at the code in my tree, ret is used uninitialized with this
> patch, so maybe coverity is wrong, or I don't have all of the needed
> patches?

The path went away when the check for debugfs_create_file() was removed.
I thought that patch was in your tree already?

In master, this is the path to "return ret" without prior assignment:

                de = debugfs_create_file(cur->name, 0644, lkdtm_debugfs_root,
                                         cur, &cur->fops);
                if (de == NULL) {
                        pr_err("could not create crashpoint %s\n", cur->name);
                        goto out_err;
                }


-- 
Kees Cook