linux-kernel - Re: [PATCH] uio.c: Fix warning: 'ret' might be used uninitialized

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Date:	Fri, 30 Nov 2012 22:39:06 +0100
From:	"Hans J. Koch" <hjk@...sjkoch.de>
To:	Vitalii Demianets <vitas@...factor.kiev.ua>
Cc:	"Hans J. Koch" <hjk@...sjkoch.de>, Tux9 <tuxding@...il.com>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] uio.c: Fix warning: 'ret' might be used uninitialized

On Fri, Nov 30, 2012 at 01:16:19PM +0200, Vitalii Demianets wrote:
> On Friday 30 November 2012 01:58:22 Hans J. Koch wrote:
> > On Thu, Nov 29, 2012 at 06:36:59PM +0200, Vitalii Demianets wrote:
> > > > On Thursday 29 November 2012 18:05:27 Tux9 wrote:
> > > > > Hans, I think there are something wrong in your patch, while
> > > > > Vitalii's is right. The variable "ret" is reused in line 292 and line
> > > > > 295, so the value of "ret" would be overridden (if it goto err_map in
> > > > > line 284 when mi>=1).
> > > >
> > > > Actually, both patches do exactly the same thing. Hans's patch
> > > > establishes default value for the ret for all those "other" cases when
> > > > ret is not explicitly overridden. My patch explicitly enumerates all
> > > > those "other" cases in more wordily manner.
> > >
> > > Oops, disregard this. After looking at it more thoroughly I got your
> > > point. You are right, ret is overridden at first iteration (mi == 0), so
> > > Hans's approach does not work.
> > > I must do more thinking before replying in a hurry.
> >
> > You're right. Initialization of "ret" has to take place at the beginning of
> > the loop.
> >
> > I think this version is right:
> 
> Yes, this looks right for me.

OK, I'll send that patch offically, then. This might also be material for
the stable updates. Greg?

Thanks a lot for reporting and discussing that problem. I'll add a

Reported-by: Vitalii Demianets <vitas@...factor.kiev.ua>

if you have no objections.

Thanks,
Hans

> 
> > >From 00c3c734c0dde67873a628bcb18cee403c95c301 Mon Sep 17 00:00:00 2001
> >
> > From: "Hans J. Koch" <hjk@...sjkoch.de>
> > Date: Fri, 30 Nov 2012 00:51:50 +0100
> > Subject: [PATCH] uio: Fix warning: 'ret' might be used uninitialized
> >
> > In two cases, the return value variable "ret" can be undefined.
> >
> > Signed-off-by: Hans J. Koch <hjk@...sjkoch.de>
> > ---
> >  drivers/uio/uio.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> > index 5110f36..0c80df2 100644
> > --- a/drivers/uio/uio.c
> > +++ b/drivers/uio/uio.c
> > @@ -273,6 +273,7 @@ static int uio_dev_add_attributes(struct uio_device
> > *idev) struct uio_portio *portio;
> >
> >  	for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
> > +		ret = -ENOMEM;
> >  		mem = &idev->info->mem[mi];
> >  		if (mem->size == 0)
> >  			break;
> > @@ -298,6 +299,7 @@ static int uio_dev_add_attributes(struct uio_device
> > *idev) }
> >
> >  	for (pi = 0; pi < MAX_UIO_PORT_REGIONS; pi++) {
> > +		ret = -ENOMEM;
> >  		port = &idev->info->port[pi];
> >  		if (port->size == 0)
> >  			break;
> 
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