linux-kernel - Re: [PATCH 1/1] x86: add phys addr validity check for /dev/mem mmap

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Date:	Thu, 14 Aug 2014 19:53:46 +0200
From:	Frantisek Hrbata <fhrbata@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Dave Hansen <dave.hansen@...el.com>, 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, dvlasenk@...hat.com,
	prarit@...hat.com, lwoodman@...hat.com, hannsj_uhl@...ibm.com
Subject: Re: [PATCH 1/1] x86: add phys addr validity check for /dev/mem mmap

On Thu, Aug 14, 2014 at 10:20:53AM -0700, H. Peter Anvin wrote:
> On 08/14/2014 09:36 AM, Dave Hansen wrote:
> > Thanks for dredging this back up!
> > 
> > On 08/14/2014 07:18 AM, Frantisek Hrbata wrote:
> >> +int valid_phys_addr_range(phys_addr_t addr, size_t count)
> >> +{
> >> +	return addr + count <= __pa(high_memory);
> >> +}
> > 
> > Is this correct on 32-bit?  It would limit /dev/mem to memory below 896MB.
> > 
> 
> Last I checked, /dev/mem was already broken for highmem... which is
> actually a problem.  I would prefer to see it fixed.
> 
> 	-hpa
> 

Hi Peter,

thank you for jumping in again. I'm not going to pretent I fully understand this
code, as proven by Dave :), but wouldn't it help just to move the high_memory
check directly to the xlate_dev_mem_ptr. Meaning no high_memory check in
valid_phys_addr_range for x86. I sent more info in my reply to Dave's mail.

Again many thanks.


-- 
Frantisek Hrbata
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