linux-kernel - Re: [RESEND PATCH] x86: add phys addr validity check for /dev/mem mmap

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Message-ID: <20131002183155.GA2975@localhost.localdomain>
Date:	Wed, 2 Oct 2013 20:31:55 +0200
From:	Frantisek Hrbata <fhrbata@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	tglx@...utronix.de, mingo@...hat.com, x86@...nel.org,
	oleg@...hat.com, kamaleshb@...ibm.com, hechjie@...ibm.com,
	akpm@...ux-foundation.org, dave.hansen@...el.com
Subject: Re: [RESEND PATCH] x86: add phys addr validity check for /dev/mem
 mmap

On Wed, Oct 02, 2013 at 10:46:35AM -0700, H. Peter Anvin wrote:
> On 10/02/2013 09:05 AM, Frantisek Hrbata wrote:
> > +
> > +int valid_phys_addr_range(phys_addr_t addr, size_t count)
> > +{
> > +	return addr + count <= __pa(high_memory);
> > +}
> > +
> > +int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
> > +{
> > +	resource_size_t addr = (pfn << PAGE_SHIFT) + count;
> > +	return phys_addr_valid(addr);
> > +}
> > 
> 
> The latter has overflow problems.

Could you please specify what overflow problems do you mean?

> 
> The former I realize matches the current /dev/mem, but it is still just
> plain wrong in multiple ways.

I guess that you are talking about /dev/mem implementation generelly, because
this patch is exactly the same as the first one. All I'm trying to do here is to
fix this simple problem, which was reported by a customer, using IMHO the least
invasive way. Anyway is there any description what is wrong with /dev/mem
implementation? Maybe I can try to take a look.

Many thanks

> 
> 	-hpa
> 

-- 
Frantisek Hrbata
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