linux-kernel - Re: [PATCH wireless-next] brcmsmac: avoid 512 byte stack variable

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Message-ID: <51140CFB.1060100@broadcom.com>
Date:	Thu, 7 Feb 2013 21:22:19 +0100
From:	"Arend van Spriel" <arend@...adcom.com>
To:	"Tim Gardner" <tim.gardner@...onical.com>
cc:	linux-kernel@...r.kernel.org,
	"Brett Rudley" <brudley@...adcom.com>,
	"Franky (Zhenhui) Lin" <frankyl@...adcom.com>,
	"Hante Meuleman" <meuleman@...adcom.com>,
	"John W. Linville" <linville@...driver.com>,
	"Seth Forshee" <seth.forshee@...onical.com>,
	"Pieter-Paul Giesberts" <pieterpg@...adcom.com>,
	"Hauke Mehrtens" <hauke@...ke-m.de>,
	linux-wireless@...r.kernel.org, brcm80211-dev-list@...adcom.com,
	netdev@...r.kernel.org, "Joe Perches" <joe@...ches.com>
Subject: Re: [PATCH wireless-next] brcmsmac: avoid 512 byte stack
 variable

On 02/07/2013 09:13 PM, Tim Gardner wrote:
> Dynamically allocate the probe response template which
> avoids potential stack corruption. Observed with smatch:
> 
> drivers/net/wireless/brcm80211/brcmsmac/main.c:7412 brcms_c_bss_update_probe_resp()
>  warn: 'prb_resp' puts 512 bytes on stack
> 
> Cc: Brett Rudley <brudley@...adcom.com>
> Cc: Arend van Spriel <arend@...adcom.com>
> Cc: "Franky (Zhenhui) Lin" <frankyl@...adcom.com>
> Cc: Hante Meuleman <meuleman@...adcom.com>
> Cc: "John W. Linville" <linville@...driver.com>
> Cc: Seth Forshee <seth.forshee@...onical.com>
> Cc: Pieter-Paul Giesberts <pieterpg@...adcom.com>
> Cc: Hauke Mehrtens <hauke@...ke-m.de>
> Cc: linux-wireless@...r.kernel.org
> Cc: brcm80211-dev-list@...adcom.com
> Cc: netdev@...r.kernel.org

One comment below. When taken care of feel free to add:

Acked-by: Arend van Spriel <arend@...adcom.com>
> Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
> ---
>  drivers/net/wireless/brcm80211/brcmsmac/main.c |   11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/brcm80211/brcmsmac/main.c b/drivers/net/wireless/brcm80211/brcmsmac/main.c
> index c26992a..e392e76 100644
> --- a/drivers/net/wireless/brcm80211/brcmsmac/main.c
> +++ b/drivers/net/wireless/brcm80211/brcmsmac/main.c
> @@ -7408,9 +7408,16 @@ brcms_c_bss_update_probe_resp(struct brcms_c_info *wlc,
>  			      struct brcms_bss_cfg *cfg,
>  			      bool suspend)
>  {
> -	u16 prb_resp[BCN_TMPL_LEN / 2];
> +	u16 *prb_resp;
>  	int len = BCN_TMPL_LEN;
>  
> +	prb_resp = kmalloc(BCN_TMPL_LEN, GFP_ATOMIC);
> +	if (!prb_resp) {
> +		wiphy_err(wlc->wiphy, "wl: %s: failed to alloc %u bytes\n",
> +			__func__, BCN_TMPL_LEN);

I believe the kmalloc() call spews enough info upon allocation failure
so please remove the error message here.

> +		return;
> +	}
> +
>  	/*
>  	 * write the probe response to hardware, or save in
>  	 * the config structure
> @@ -7444,6 +7451,8 @@ brcms_c_bss_update_probe_resp(struct brcms_c_info *wlc,
>  
>  	if (suspend)
>  		brcms_c_enable_mac(wlc);
> +
> +	kfree(prb_resp);
>  }
>  
>  void brcms_c_update_probe_resp(struct brcms_c_info *wlc, bool suspend)
> 


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