netdev - Re: [PATCH] brcmsmac: don't leak kernel memory via printk()

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Date:	Wed, 17 Dec 2014 22:32:04 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	"John W. Linville" <linville@...driver.com>,
	Kalle Valo <kvalo@....qualcomm.com>,
	"David S. Miller" <davem@...emloft.net>
Cc:	Brian Norris <computersforpeace@...il.com>,
	Brett Rudley <brudley@...adcom.com>,
	Arend van Spriel <arend@...adcom.com>,
	"Franky (Zhenhui) Lin" <frankyl@...adcom.com>,
	Hante Meuleman <meuleman@...adcom.com>,
	linux-wireless@...r.kernel.org, brcm80211-dev-list@...adcom.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH] brcmsmac: don't leak kernel memory via printk()

+ others [1]

On Wed, Dec 10, 2014 at 1:39 AM, Brian Norris
<computersforpeace@...il.com> wrote:
> Debug code prints the fifo name via custom dev_warn() wrappers. The
> fifo_names array is only non-zero when debugging is manually enabled,
> which is all well and good. However, it's *not* good that this array
> uses zero-length arrays in the non-debug case, and so it doesn't
> actually have any memory allocated to it. This means that as far as we
> know, fifo_names[i] actually points to garbage memory.
>
> I've seen this in my log:
>
> [ 4601.205511] brcmsmac bcma0:1: wl0: brcms_c_d11hdrs_mac80211: �GeL txop exceeded phylen 137/256 dur 1602/1504
>
> So let's give this array space enough to fill it with a NULL byte.
>
> Signed-off-by: Brian Norris <computersforpeace@...il.com>
> 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: linux-wireless@...r.kernel.org
> Cc: brcm80211-dev-list@...adcom.com
> Cc: netdev@...r.kernel.org

BTW, I guess this qualifies as a security hole, albeit a small one.
Should this be CC: stable@...r.kernel.org?

> ---
>  drivers/net/wireless/brcm80211/brcmsmac/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/wireless/brcm80211/brcmsmac/main.c b/drivers/net/wireless/brcm80211/brcmsmac/main.c
> index 1b474828d5b8..aed0c948dce8 100644
> --- a/drivers/net/wireless/brcm80211/brcmsmac/main.c
> +++ b/drivers/net/wireless/brcm80211/brcmsmac/main.c
> @@ -316,7 +316,7 @@ static const u16 xmtfifo_sz[][NFIFO] = {
>  static const char * const fifo_names[] = {
>         "AC_BK", "AC_BE", "AC_VI", "AC_VO", "BCMC", "ATIM" };
>  #else
> -static const char fifo_names[6][0];
> +static const char fifo_names[6][1];
>  #endif
>
>  #ifdef DEBUG

Brian

[1] http://lwn.net/Articles/626689/
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