linux-kernel - Re: [PATCH v2] sparc: kernel/sbus.c: fix memory leakage

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Date:	Thu, 17 Jan 2013 13:16:04 +0000
From:	Cong Ding <dinggnu@...il.com>
To:	Richard Mortimer <richm@...elvet.org.uk>
Cc:	Sam Ravnborg <sam@...nborg.org>,
	"David S. Miller" <davem@...emloft.net>,
	sparclinux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sparc: kernel/sbus.c: fix memory leakage

On Thu, Jan 17, 2013 at 12:30:11PM +0000, Richard Mortimer wrote:
> 
> 
> On 17/01/2013 11:56, Cong Ding wrote:
> >On Thu, Jan 17, 2013 at 10:41:59AM +0000, Richard Mortimer wrote:
> >>
> >>
> >>On 16/01/2013 22:01, Cong Ding wrote:
> >>>the variable iommu and strbuf are not freed if it goes to error.
> >>>
> >>>Signed-off-by: Cong Ding <dinggnu@...il.com>
> >>>---
> >>>  arch/sparc/kernel/sbus.c |    2 ++
> >>>  1 file changed, 2 insertions(+)
> >>>
> >>>diff --git a/arch/sparc/kernel/sbus.c b/arch/sparc/kernel/sbus.c
> >>>index 1271b3a..78aa26b 100644
> >>>--- a/arch/sparc/kernel/sbus.c
> >>>+++ b/arch/sparc/kernel/sbus.c
> >>>@@ -656,6 +656,8 @@ static void __init sbus_iommu_init(struct platform_device *op)
> >>>  	return;
> >>>
> >>>  fatal_memory_error:
> >>>+	kfree(strbuf);
> >>
> >>strbuf will be uninitialized if the iommu allocation fails. I don't
> >>have a particular preference for how to fix this but tend to dislike
> >>initial assignment with NULL because it hides other control flow
> >>issues.
> >Sorry I didn't notice strbuf will be uninitialized here. But if we don't
> >initially assign a NULL value to strbuf, I cannot find a way to handle it
> >besides the first version patch. Did you have any suggestions? For me, I like
> >the first version.
> 
> Two thoughts...
> 
> 1 - just use a goto target for the iommu allocation failure and make
> that skip the strbuf free call. The others use the existing
> fatal_memory_error label.
this looks ugly. If we do in this way, why not version 1?
> 
> 2 - Move the strbuf kzalloc up 2 lines so that it occurs before the
> test for iommu.
> 
> 2b - In case (2) above the failure test could be changed to
> if (!iommu || !strbuf)
> to remove duplication of goto.
I will send a new version by using this solution.
Thanks, - cong

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