Re: [RFC] [PATCH]: ACPI: Rename ACPI processor device bus ID

Henrique de Moraes Holschuh
2009-05-23T21:01:58Z

On Sat, 23 May 2009, yakui_zhao wrote:
> On Sat, 2009-05-23 at 11:18 +0800, Henrique de Moraes Holschuh wrote:
> > On Thu, 21 May 2009, yakui_zhao wrote:
> > > + sprintf(acpi_device_bid(device), "CPU%X", pr->id);
> >
> > Is this safe against overflows, i.e. is pr->id something *we* set? Because
> > if it is in any way read from the ACPI firmware, you have to either use
> > snprintf, or use the format string to limit the %X to a safe lenght...
> Thanks for pointing out this issue.
> Now the array size of acpi_bus_id is 5. And when the cpu number is above
> 256, the overflow will happen. But it is very luck that the following
> three bytes are not used by other variable because of align. And this
> still can work.
> Of course I already sent a patch, in which the array size is changed
> from 5 to 8.
>
> At the same time if the cpu number is less than or equal to 256, the
> length of format string is safe.

Yeah, but I was really asking if, even with space for 8 chars, isn't there a
risk of pr->id being, say, 0xfffffffe due to some wierdness...

If there is such a risk, you should use snprintf, or a a length limit in the
format...

--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh