Messages in this thread | | | Date | Tue, 12 Jan 2021 12:00:28 +0100 | From | Oscar Salvador <> | Subject | Re: [PATCH v2 3/5] mm: Teach pfn_to_online_page() about ZONE_DEVICE section collisions |
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On Tue, Jan 12, 2021 at 01:34:53AM -0800, Dan Williams wrote: > While pfn_to_online_page() is able to determine pfn_valid() at > subsection granularity it is not able to reliably determine if a given > pfn is also online if the section is mixes ZONE_{NORMAL,MOVABLE} with > ZONE_DEVICE. This means that pfn_to_online_page() may return invalid > @page objects. For example with a memory map like: > > 100000000-1fbffffff : System RAM > 142000000-143002e16 : Kernel code > 143200000-143713fff : Kernel rodata > 143800000-143b15b7f : Kernel data > 144227000-144ffffff : Kernel bss > 1fc000000-2fbffffff : Persistent Memory (legacy) > 1fc000000-2fbffffff : namespace0.0 > > This command: > > echo 0x1fc000000 > /sys/devices/system/memory/soft_offline_page > > ...succeeds when it should fail. When it succeeds it touches > an uninitialized page and may crash or cause other damage (see > dissolve_free_huge_page()).
[...]
> Because the collision case is rare, and for simplicity, the > SECTION_TAINT_ZONE_DEVICE flag is never cleared once set. > > Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") > Cc: Andrew Morton <akpm@linux-foundation.org> > Reported-by: Michal Hocko <mhocko@suse.com> > Reported-by: David Hildenbrand <david@redhat.com> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
-- Oscar Salvador SUSE L3
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