On Tue, Jan 12, 2021 at 11:35:27PM -0800, Dan Williams wrote:
> pfn_section_valid() determines pfn validity on subsection granularity
> where pfn_valid() may be limited to coarse section granularity.
> Explicitly validate subsections after pfn_valid() succeeds.
>
> Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()")
> Cc: Qian Cai <cai@xxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Reported-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
> ---
> mm/memory_hotplug.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 55a69d4396e7..9f37f8a68da4 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -308,11 +308,27 @@ static int check_hotplug_memory_addressable(unsigned long pfn,
> struct page *pfn_to_online_page(unsigned long pfn)
> {
> unsigned long nr = pfn_to_section_nr(pfn);
> + struct mem_section *ms;
> +
> + if (nr >= NR_MEM_SECTIONS)
> + return NULL;
> +
> + ms = __nr_to_section(nr);
> + if (!online_section(ms))
> + return NULL;
> +
> + /*
> + * Save some code text when online_section() +
> + * pfn_section_valid() are sufficient.
> + */
> + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID))
> + if (!pfn_valid(pfn))
> + return NULL;
> +
> + if (!pfn_section_valid(ms, pfn))
> + return NULL;
>
> - if (nr < NR_MEM_SECTIONS && online_section_nr(nr) &&
> - pfn_valid_within(pfn))
> - return pfn_to_page(pfn);
> - return NULL;
> + return pfn_to_page(pfn);
> }
> EXPORT_SYMBOL_GPL(pfn_to_online_page);
>
>
--
Oscar Salvador
SUSE L3
