Messages in this thread | | | Date | Wed, 02 Oct 2013 11:36:09 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [RESEND PATCH] x86: add phys addr validity check for /dev/mem mmap |
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On 10/02/2013 11:31 AM, Frantisek Hrbata wrote: > 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?
Consider if pfn + count overflows and wraps around, or if (pfn << PAGE_SHIFT) pushes bits out to the left.
>> 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. >
The bottom line is that read/write to /dev/mem should be able to access the same memory that we can mmap(). Having two different tests is ridiculous.
-hpa
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