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mm/memory_hotplug.c: add a bounds check to __add_pages() 

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 4ffe713b75 ("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

Link: http://lkml.kernel.org/r/20191001004617.7536-2-alastair@au1.ibm.com
Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alastair D'Silva 2019-11-30 17:53:48 -08:00 committed by Linus Torvalds
parent 32d1fe8fcb
commit dca4436d1c
1 changed files with 20 additions and 0 deletions
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20
mm/memory_hotplug.c
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@ -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)
{
const u64 max_addr = PFN_PHYS(pfn + nr_pages) - 1;
if (max_addr >> MAX_PHYSMEM_BITS) {
const u64 max_allowed = (1ull << (MAX_PHYSMEM_BITS + 1)) - 1;
WARN(1,
"Hotplugged memory exceeds maximum addressable address, range=%#llx-%#llx, maximum=%#llx\n",
(u64)PFN_PHYS(pfn), max_addr, max_allowed);
return -E2BIG;
}
return 0;
}
/*
* Reasonably generic function for adding memory. It is
* expected that archs that support memory hotplug will
@ -291,6 +307,10 @@ int __ref __add_pages(int nid, unsigned long pfn, unsigned long nr_pages,
unsigned long nr, start_sec, end_sec;
struct vmem_altmap *altmap = restrictions->altmap;
err = check_hotplug_memory_addressable(pfn, nr_pages);
if (err)
return err;
if (altmap) {
/*
* Validate altmap is within bounds of the total request