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Re: Possible broken MM code in dell-laptop.c?

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  Re: Possible broken MM code in dell-laptop.c? Darren Hart <dvhart@infradead.org> - 2015-06-15 22:40 +0200
    Re: Possible broken MM code in dell-laptop.c? Pali Rohár <pali.rohar@gmail.com> - 2015-06-15 22:50 +0200

#1165541 — Re: Possible broken MM code in dell-laptop.c?

On Sun, Jun 14, 2015 at 11:05:07AM +0200, Pali Rohár wrote:
> Hello,
> 
> in drivers/platform/x86/dell-laptop.c is this part of code:
> 
> static int __init dell_init(void)
> {
> ...
> 	/*
> 	 * Allocate buffer below 4GB for SMI data--only 32-bit physical addr
> 	 * is passed to SMI handler.
> 	 */
> 	bufferpage = alloc_page(GFP_KERNEL | GFP_DMA32);
> 	if (!bufferpage) {
> 		ret = -ENOMEM;
> 		goto fail_buffer;
> 	}
> 	buffer = page_address(bufferpage);
> 
> 	ret = dell_setup_rfkill();
> 
> 	if (ret) {
> 		pr_warn("Unable to setup rfkill\n");
> 		goto fail_rfkill;
> 	}
> ...
> fail_rfkill:
> 	free_page((unsigned long)bufferpage);
> fail_buffer:
> ...
> }
> 
> Then there is another part:
> 
> static void __exit dell_exit(void)
> {
> ...
> 	free_page((unsigned long)buffer);

I believe you are correct, and this should be bufferpage. Have you observed any
failures?

-- 
Darren Hart
Intel Open Source Technology Center
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#1165544

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On Monday 15 June 2015 22:36:45 Darren Hart wrote:
> On Sun, Jun 14, 2015 at 11:05:07AM +0200, Pali Rohár wrote:
> > Hello,
> > 
> > in drivers/platform/x86/dell-laptop.c is this part of code:
> > 
> > static int __init dell_init(void)
> > {
> > ...
> > 
> > 	/*
> > 	
> > 	 * Allocate buffer below 4GB for SMI data--only 32-bit physical
> > 	 addr * is passed to SMI handler.
> > 	 */
> > 	
> > 	bufferpage = alloc_page(GFP_KERNEL | GFP_DMA32);
> > 	if (!bufferpage) {
> > 	
> > 		ret = -ENOMEM;
> > 		goto fail_buffer;
> > 	
> > 	}
> > 	buffer = page_address(bufferpage);
> > 	
> > 	ret = dell_setup_rfkill();
> > 	
> > 	if (ret) {
> > 	
> > 		pr_warn("Unable to setup rfkill\n");
> > 		goto fail_rfkill;
> > 	
> > 	}
> > 
> > ...
> > 
> > fail_rfkill:
> > 	free_page((unsigned long)bufferpage);
> > 
> > fail_buffer:
> > ...
> > }
> > 
> > Then there is another part:
> > 
> > static void __exit dell_exit(void)
> > {
> > ...
> > 
> > 	free_page((unsigned long)buffer);
> 
> I believe you are correct, and this should be bufferpage. Have you
> observed any failures?

Rmmoding dell-laptop.ko works fine. There is no error in dmesg. I think 
that buffer (and not bufferpage) should be passed to free_page(). So in 
my opinion problem is at fail_rfkill: label and not in dell_exit().

But somebody from linux-mm should look at it...

-- 
Pali Rohár
pali.rohar@gmail.com

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