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

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Message-ID: <20121129235822.GA2590@local>
Date:	Fri, 30 Nov 2012 00:58:22 +0100
From:	"Hans J. Koch" <hjk@...sjkoch.de>
To:	Vitalii Demianets <vitas@...factor.kiev.ua>
Cc:	Tux9 <tuxding@...il.com>, "Hans J. Koch" <hjk@...sjkoch.de>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] uio.c: Fix warning: 'ret' might be used uninitialized

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:


>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;
-- 
1.7.9

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