On Thu, Sep 26, 2019 at 11:34:05AM +1000, Alastair D'Silva wrote:
> From: Alastair D'Silva <alast...@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-alast...@au1.ibm.com
>
> Signed-off-by: Alastair D'Silva <alast...@d-silva.org>
Reviewed-by: Oscar Salvador <osalva...@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
