Messages in this thread | | | Date | Thu, 26 Sep 2019 09:53:07 +0200 | From | Oscar Salvador <> | Subject | Re: [PATCH v4] memory_hotplug: Add a bounds check to __add_pages |
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On Thu, Sep 26, 2019 at 11:34:05AM +1000, Alastair D'Silva wrote: > From: Alastair D'Silva <alastair@d-silva.org> > > On PowerPC, the address ranges allocated to OpenCAPI LPC memory > are allocated from firmware. These address ranges may be higher > than what older kernels permit, as we increased the maximum > permissable address in commit 4ffe713b7587 > ("powerpc/mm: Increase the max addressable memory to 2PB"). It is > possible that the addressable range may change again in the > future. > > In this scenario, we end up with a bogus section returned from > __section_nr (see the discussion on the thread "mm: Trigger bug on > if a section is not found in __section_nr"). > > Adding a check here means that we fail early and have an > opportunity to handle the error gracefully, rather than rumbling > on and potentially accessing an incorrect section. > > Further discussion is also on the thread ("powerpc: Perform a bounds > check in arch_add_memory") > http://lkml.kernel.org/r/20190827052047.31547-1-alastair@au1.ibm.com > > Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Just a nit-picking below:
> --- > mm/memory_hotplug.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index c73f09913165..212804c0f7f5 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -278,6 +278,22 @@ static int check_pfn_span(unsigned long pfn, unsigned long nr_pages, > return 0; > } > > +static int check_hotplug_memory_addressable(unsigned long pfn, > + unsigned long nr_pages) > +{ > + unsigned long max_addr = ((pfn + nr_pages) << PAGE_SHIFT) - 1;
I would use PFN_PHYS instead:
unsigned long max_addr = PFN_PHYS(pfn + nr_pages) - 1;
> + > + if (max_addr >> MAX_PHYSMEM_BITS) { > + WARN(1, > + "Hotplugged memory exceeds maximum addressable address, range=%#lx-%#lx, maximum=%#lx\n", > + pfn << PAGE_SHIFT, max_addr,
Same here.
> + (1ul << (MAX_PHYSMEM_BITS + 1)) - 1);
I would use a local variable to hold this computation.
> + return -E2BIG; > + } > + > + return 0;
-- Oscar Salvador SUSE L3
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