linux-kernel - Re: [PATCH] drivers/acpi/ec.c fix a small memory leak

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Message-ID: <20100203061225.GB32535@bicker>
Date:	Wed, 3 Feb 2010 09:12:26 +0300
From:	Dan Carpenter <error27@...il.com>
To:	Alexey Starikovskiy <astarikovskiy@...e.de>
Cc:	Darren Jenkins <darrenrjenkins@...il.com>,
	Kernel Janitors <kernel-janitors@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	linux ACPI <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers/acpi/ec.c fix a small memory leak

On Tue, Feb 02, 2010 at 06:35:44PM +0300, Alexey Starikovskiy wrote:
> NAK
> 
> saved_ec is allocated if flag EC_FLAGS_VALIDATE_ECDT is true.
> EC_FLAGS_SKIP_DSDT_SCAN have no sense in such case, thus this new code path
> is never executed.
> On the other hand, unconditionally freeing pointer, which is might be NULL, is not
> right either.

As near as I can tell you are right that the code cannot leak memory.  But Darren 
is right to think that it's calling kfree() on a NULL pointer is OK.  His patch does 
not introduce any errors.

The logic here is basically spaghetti.  Every person who looks at it is going to 
think it's a leak.  Lots of people are going to look at it, because the static
checkers all think it's a leak too.  Someone could send a cleanup patch that makes it
readable.

regards,
dan carpenter

> So, this patch introduced more problems as it tries to solve...
> 
> Regards,
> Alex.
> 
> Darren Jenkins пишет:
> > Plug a very small leak in acpi_ec_ecdt_probe()
> > 
> > Coverity CID: 13319
> > 
> > Signed-off-by: Darren Jenkins <darrenrjenkins@...il.com> 
> > 
> > diff --git drivers/acpi/ec.c drivers/acpi/ec.c
> > index d6471bb..13061dc 100644
> > --- drivers/acpi/ec.c
> > +++ drivers/acpi/ec.c
> > @@ -1009,8 +1009,10 @@ int __init acpi_ec_ecdt_probe(void)
> >  	/* fall through */
> >  	}
> >  
> > -	if (EC_FLAGS_SKIP_DSDT_SCAN)
> > +	if (EC_FLAGS_SKIP_DSDT_SCAN) {
> > +		kfree(saved_ec);
> >  		return -ENODEV;
> > +	}
> >  
> >  	/* This workaround is needed only on some broken machines,
> >  	 * which require early EC, but fail to provide ECDT */
> > 
> > 
> 
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