linux-kernel - Re: [PATCH] Libertas: fix buffer overflow in lbs_get

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Message-Id: <1260982667.2179.9.camel@localhost.localdomain>
Date:	Wed, 16 Dec 2009 08:57:47 -0800
From:	Dan Williams <dcbw@...hat.com>
To:	Daniel Mack <daniel@...aq.de>
Cc:	linux-kernel@...r.kernel.org,
	Holger Schurig <holgerschurig@...il.com>,
	"John W. Linville" <linville@...driver.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	Maithili Hinge <maithili@...vell.com>,
	Kiran Divekar <dkiran@...vell.com>,
	Michael Hirsch <m.hirsch@...mfeld.com>, netdev@...r.kernel.org,
	libertas-dev@...ts.infradead.org,
	linux-wireless@...ts.infradead.org, stable@...nel.org
Subject: Re: [PATCH] Libertas: fix buffer overflow in lbs_get_essid()

On Wed, 2009-12-16 at 05:12 +0100, Daniel Mack wrote:
> The libertas driver copies the SSID buffer back to the wireless core and
> appends a trailing NULL character for termination. This is
> 
> a) unnecessary because the buffer is allocated with kzalloc and is hence
>    already NULLed when this function is called, and
> 
> b) for priv->curbssparams.ssid_len == 32, it writes back one byte too
>    much which causes memory corruptions.
> 
> Fix this by removing the extra write.

Acked-by: Dan Williams <dcbw@...hat.com>

> Signed-off-by: Daniel Mack <daniel@...aq.de>
> Cc: Dan Williams <dcbw@...hat.com>
> Cc: Holger Schurig <holgerschurig@...il.com>
> Cc: John W. Linville <linville@...driver.com>
> Cc: Stephen Hemminger <shemminger@...tta.com>
> Cc: Maithili Hinge <maithili@...vell.com>
> Cc: Kiran Divekar <dkiran@...vell.com>
> Cc: Michael Hirsch <m.hirsch@...mfeld.com>
> Cc: netdev@...r.kernel.org
> Cc: libertas-dev@...ts.infradead.org
> Cc: linux-wireless@...ts.infradead.org
> Cc: stable@...nel.org
> ---
>  drivers/net/wireless/libertas/wext.c |    2 --
>  1 files changed, 0 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/libertas/wext.c b/drivers/net/wireless/libertas/wext.c
> index be837a0..01c738b 100644
> --- a/drivers/net/wireless/libertas/wext.c
> +++ b/drivers/net/wireless/libertas/wext.c
> @@ -1953,10 +1953,8 @@ static int lbs_get_essid(struct net_device *dev, struct iw_request_info *info,
>  	if (priv->connect_status == LBS_CONNECTED) {
>  		memcpy(extra, priv->curbssparams.ssid,
>  		       priv->curbssparams.ssid_len);
> -		extra[priv->curbssparams.ssid_len] = '\0';
>  	} else {
>  		memset(extra, 0, 32);
> -		extra[priv->curbssparams.ssid_len] = '\0';
>  	}
>  	/*
>  	 * If none, we may want to get the one that was set

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