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

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Message-ID: <515B3F98.5020101@zytor.com>
Date:	Tue, 02 Apr 2013 13:29:12 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Frantisek Hrbata <fhrbata@...hat.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
Subject: Re: [PATCH] x86: add phys addr validity check for /dev/mem mmap

On 04/02/2013 12:10 PM, Frantisek Hrbata wrote:
> 
> Hi, this is exactly what the patch is doing imho. Note that the
> valid_phys_addr_range(), which is using the high_memory, is the same as the
> default one in drivers/char/mem.c(#ifndef ARCH_HAS_VALID_PHYS_ADDR_RANGE). I
> just added x86 specific check for valid_mmap_phys_addr_range and moved both
> functions to arch/x86/mm/mmap.c, rather then modifying the default generic ones.
> This is how other archs(arm) are doing it.
> 
> Also valid_phys_addr_range is used just in read|write_mem and
> valid_mmap_phys_addr_range is checked in mmap_mem and it calls phys_addr_valid
> 
> static inline int phys_addr_valid(resource_size_t addr)
> {
> #ifdef CONFIG_PHYS_ADDR_T_64BIT
> 	return !(addr >> boot_cpu_data.x86_phys_bits);
> #else
>         return 1;
> #endif
> }                          
> 
> I for sure could overlooked something, but this seems right to me.
> 

OK, this is really confusing ... which isn't a *huge* surprise (the
entire /dev/mem code has some gigantic bugs in it.)

I think I need to do more of an in-depth review.  The other question is
why we don't call phys_addr_valid() everywhere.

	-hpa


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