linux-kernel - Re: [PATCH resend 3/5] libata-scsi: fix overflow in mode page copy

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Message-ID: <20160721211714.GE23759@htj.duckdns.org>
Date:	Thu, 21 Jul 2016 17:17:14 -0400
From:	Tejun Heo <tj@...nel.org>
To:	tom.ty89@...il.com
Cc:	hare@...e.de, sergei.shtylyov@...entembedded.com, arnd@...db.de,
	sfr@...b.auug.org.au, linux-ide@...r.kernel.org,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-next@...r.kernel.org
Subject: Re: [PATCH resend 3/5] libata-scsi: fix overflow in mode page copy

Hello,

On Fri, Jul 22, 2016 at 02:41:52AM +0800, tom.ty89@...il.com wrote:
> From: Tom Yan <tom.ty89@...il.com>
> 
> ata_mselect_*() would initialize a char array for storing a copy of
> the current mode page. However, if char was actually signed char,
> overflow could occur.

Do you mean sign extension?

> For example, `0xff` from def_control_mpage[] would be "truncated"
> to `-1`. This prevented ata_mselect_control() from working at all,
> since when it did the read-only bits check, there would always be
> a mismatch.

Heh, the description doesn't really make sense.  Are you talking about
something like the following?

	char ar[N];
	int i;

	i = ar[x];
	if (i == 0xff)
		asdf;

If so, the description isn't quite right.

Thanks.

-- 
tejun