linux-kernel - Re: [PATCH] pxa: make index mfp unsigned in mfp

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Message-ID: <4AFD36EE.6030509@gmail.com>
Date:	Fri, 13 Nov 2009 11:37:34 +0100
From:	Roel Kluin <roel.kluin@...il.com>
To:	Eric Miao <eric.y.miao@...il.com>
CC:	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pxa: make index mfp unsigned in mfp_read() and write()

Ensure we do not read/write outside array boundaries
with a negative index.

Signed-off-by: Roel Kluin <roel.kluin@...il.com>
---
On 13-11-09 08:03, Eric Miao wrote:
> On Thu, Nov 12, 2009 at 12:05 AM, Roel Kluin <roel.kluin@...il.com> wrote:
>> When signed, it is possible in theory to pass a negative mfp,
>> and read/write outside the array bounds.

>> I did not observe the passing of a negative mfp anywhere so this
>> can be considered as a cleanup. Alternatively I could introduce
>> a `mfp < 0' check in mfp_{read,write} instead if desired.
>>
> 
> I'd prefer to have a check in mfp_{read,write} instead.

ok,

diff --git a/arch/arm/plat-pxa/mfp.c b/arch/arm/plat-pxa/mfp.c
index 9405d03..be58f9f 100644
--- a/arch/arm/plat-pxa/mfp.c
+++ b/arch/arm/plat-pxa/mfp.c
@@ -207,7 +207,7 @@ unsigned long mfp_read(int mfp)
 {
 	unsigned long val, flags;
 
-	BUG_ON(mfp >= MFP_PIN_MAX);
+	BUG_ON(mfp < 0 || mfp >= MFP_PIN_MAX);
 
 	spin_lock_irqsave(&mfp_spin_lock, flags);
 	val = mfpr_readl(mfp_table[mfp].mfpr_off);
@@ -220,7 +220,7 @@ void mfp_write(int mfp, unsigned long val)
 {
 	unsigned long flags;
 
-	BUG_ON(mfp >= MFP_PIN_MAX);
+	BUG_ON(mfp < 0 || mfp >= MFP_PIN_MAX);
 
 	spin_lock_irqsave(&mfp_spin_lock, flags);
 	mfpr_writel(mfp_table[mfp].mfpr_off, val);
--
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