netdev - Re: [RFC PATCH] rtl8187: Fix led support for rfkill

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Date:	Thu, 31 Mar 2011 14:19:03 -0300
From:	Herton Ronaldo Krzesinski <herton.krzesinski@...onical.com>
To:	wu zhangjin <wuzhangjin@...il.com>
Cc:	Larry Finger <Larry.Finger@...inger.net>,
	Hin-Tak Leung <htl10@...rs.sourceforge.net>,
	Herton Ronaldo Krzesinski <herton@...onical.com>,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	Roman Mamedov <rm@...anrm.ru>
Subject: Re: [RFC PATCH] rtl8187: Fix led support for rfkill

On Fri, Apr 01, 2011 at 12:22:51AM +0800, wu zhangjin wrote:
> On Mon, Mar 28, 2011 at 11:40 PM, Herton Ronaldo Krzesinski
> <herton.krzesinski@...onical.com> wrote:
> [...]
> >>
> >> My rtl8187 devices are both external USB sticks, thus they have no
> >> interaction with a radio-kill switch. I will test your patch to make
> >> sure it does no harm to my system.
> >>
> >> I think the commit message should be revised. A simple statement
> >> like "the LED does not turn off when the rfkill switch is off"
> >> should be sufficient.
> >
> > The patch should work, but I wonder if we should be fiddling with priv->vif
> > for this, perhaps we should not assume vif to be valid after
> > rtl8187_remove_interface (I don't see problems with current
> > rtl8187/mac80211 code on a quick look, but...)
> >
> 
> Yes, but seems only two places have touched the vif pointer.
> 
> $ grep "vif =" -ur drivers/net/wireless/rtl818x/rtl8187/
> drivers/net/wireless/rtl818x/rtl8187/dev.c:	priv->vif = NULL;
> drivers/net/wireless/rtl818x/rtl8187/dev.c:	priv->vif = vif;
> 
> > I cleaner solution may be to use a priv->mode like p54.
> 
> Yep, then, we may need to add a 'mode' member to rtl8187_priv and
> update it properly like p54.
> 
> So, What do you prefer? I will prepare a new patch asap.

In the led code we dereference priv->vif, checking for priv->vif->type.
vif is a pointer from mac80211, and after rtl8187_remove_interface is
called by it, at least from my POV can do anything it wants with vif,
like freeing the sdata vif points to. From what I checked, it doesn't
free currently and your patch don't have issues, but may be it's better
to be safe and add a new "future proof" mode field.

And as your bug shows, the led code access priv->vif after
rtl8187_remove_interface, so we hit the case where vif could be
considered invalid.

So because of this and being cleaner I would go adding 'mode'.

> 
> Best Regards,
> Wu Zhangjin
> 
> >
> >>
> >> Larry
> >>
> >
> > --
> > []'s
> > Herton
> >
> 

-- 
[]'s
Herton
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