linux-kernel - RE: [PATCH RFC 1/6] net: rfkill: gpio: fix gpio name buffer size off by 1

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Date:	Fri, 17 Jan 2014 09:46:08 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Chen-Yu Tsai' <wens@...e.org>,
	Johannes Berg <johannes@...solutions.net>,
	"David S. Miller" <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-sunxi@...glegroups.com" <linux-sunxi@...glegroups.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>
Subject: RE: [PATCH RFC 1/6] net: rfkill: gpio: fix gpio name buffer size
 off by 1

From: Chen-Yu Tsai
> snprintf should be passed the complete size of the buffer, including
> the space for '\0'. The previous code resulted in the *_reset and
> *_shutdown strings being truncated.
...
> diff --git a/net/rfkill/rfkill-gpio.c b/net/rfkill/rfkill-gpio.c
...
> -	snprintf(rfkill->reset_name, len + 6 , "%s_reset", rfkill->name);
> -	snprintf(rfkill->shutdown_name, len + 9, "%s_shutdown", rfkill->name);
> +	snprintf(rfkill->reset_name, len + 7 , "%s_reset", rfkill->name);
> +	snprintf(rfkill->shutdown_name, len + 10, "%s_shutdown", rfkill->name);

I can't find the context for the above, but they look very dubious.
I'd expect: snprintf(foo, sizeof foo, ...).
If you are trying to truncate rfkill->name you need to use %.*s.

	David



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