linux-kernel - Re: [PATCH 1/3] dell-laptop: Clear buffer before each SMBIOS call

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Date:	Fri, 3 Jul 2015 10:10:38 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Darren Hart <dvhart@...radead.org>
Cc:	Matthew Garrett <mjg59@...f.ucam.org>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	Gabriele Mazzotta <gabriele.mzt@...il.com>
Subject: Re: [PATCH 1/3] dell-laptop: Clear buffer before each SMBIOS call

On Wednesday 01 July 2015 17:45:44 Darren Hart wrote:
> On Wed, Jul 01, 2015 at 08:08:19PM +0200, Pali Rohár wrote:
> > Make sure that before initializing SMBIOS call input buffer does not contain
> > any garbage (e.g values from previous SMBIOS call). This fix problem with
> > passing undefined/random parameters to SMBIOS functions.
> > 
> > Signed-off-by: Pali Rohár <pali.rohar@...il.com>
> > ---
> >  drivers/platform/x86/dell-laptop.c |   11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> > index 35758cb..6728487 100644
> > --- a/drivers/platform/x86/dell-laptop.c
> > +++ b/drivers/platform/x86/dell-laptop.c
> > @@ -310,10 +310,15 @@ static DEFINE_MUTEX(buffer_mutex);
> >  
> >  static int hwswitch_state;
> >  
> > +static void clear_buffer(void)
> > +{
> > +	memset(buffer, 0, sizeof(struct calling_interface_buffer));
> > +}
> > +
> >  static void get_buffer(void)
> >  {
> >  	mutex_lock(&buffer_mutex);
> > -	memset(buffer, 0, sizeof(struct calling_interface_buffer));
> > +	clear_buffer();
> >  }
> >  
> >  static void release_buffer(void)
> > @@ -557,6 +562,8 @@ static int dell_rfkill_set(void *data, bool blocked)
> >  	    !(buffer->output[1] & BIT(16)))
> >  		disable = 1;
> >  
> > +	clear_buffer();
> > +
> >  	buffer->input[0] = (1 | (radio<<8) | (disable << 16));
> >  	dell_send_request(buffer, 17, 11);
> >  
> > @@ -571,6 +578,7 @@ static void dell_rfkill_update_sw_state(struct rfkill *rfkill, int radio,
> >  	if (status & BIT(0)) {
> >  		/* Has hw-switch, sync sw_state to BIOS */
> >  		int block = rfkill_blocked(rfkill);
> > +		clear_buffer();
> >  		buffer->input[0] = (1 | (radio << 8) | (block << 16));
> >  		dell_send_request(buffer, 17, 11);
> >  	} else {
> > @@ -774,6 +782,7 @@ static int __init dell_setup_rfkill(void)
> >  	dell_send_request(buffer, 17, 11);
> >  	status = buffer->output[1];
> >  	buffer->input[0] = 0x2;
> > +	clear_buffer();
> >  	dell_send_request(buffer, 17, 11);
> 
> This clears the buffer after modifying input[0] and right before
> dell_send_request... so you're sending a completely empty buffer? Is that
> intentional here? I guess I would have expected the clear_buffer to be one line
> earlier.
> 

Yes, now I see. I split that one patch into tree and I checked that
every one compiles fine and cumulative change of all patches is same...
Because that part (sending 0x2) is deleted in patch 3/3 it missed in my
eyes...

I will fix these problems and sent patch series again.

> >  	hwswitch_state = buffer->output[1];
> >  	release_buffer();
> > -- 
> > 1.7.9.5
> > 
> > 
> 

-- 
Pali Rohár
pali.rohar@...il.com
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