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

Pali Rohár
2015-06-15T21:28:08Z

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On Monday 15 June 2015 23:18:16 Michal Hocko wrote:
> On Sun 14-06-15 11:05:07, 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);
>
> [...]
>
> > buffer = page_address(bufferpage);
>
> [...]
>
> > fail_rfkill:
> > free_page((unsigned long)bufferpage);
>
> This one should be __free_page because it consumes struct page* and
> it is the proper counter part for alloc_page. free_page, just to
> make it confusing, consumes an address which has to be translated to
> a struct page.
>
> I have no idea why the API has been done this way and yeah, it is
> really confusing.
>
> [...]
>
> > static void __exit dell_exit(void)
> > {
> > ...
> >
> > free_page((unsigned long)buffer);

So both, either:

free_page((unsigned long)buffer);

or

__free_page(bufferpage);

is correct?

--
Pali Rohár
pali.rohar@gmail.com

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