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mm/page_alloc: don't call pfn_to_page() on possibly non-existent PFN in split_large_buddy()

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In split_large_buddy(), we might call pfn_to_page() on a PFN that might
not exist.  In corner cases, such as when freeing the highest pageblock in
the last memory section, this could result with CONFIG_SPARSEMEM &&
!CONFIG_SPARSEMEM_EXTREME in __pfn_to_section() returning NULL and and
__section_mem_map_addr() dereferencing that NULL pointer.

Let's fix it, and avoid doing a pfn_to_page() call for the first
iteration, where we already have the page.

So far this was found by code inspection, but let's just CC stable as the
fix is easy.

Link: https://lkml.kernel.org/r/20241210093437.174413-1-david@redhat.com
Fixes: fd919a85cd ("mm: page_isolation: prepare for hygienic freelists")
Signed-off-by: David Hildenbrand <david@redhat.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Closes: https://lkml.kernel.org/r/e1a898ba-a717-4d20-9144-29df1a6c8813@suse.cz
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yu Zhao <yuzhao@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Hildenbrand 2024-12-10 10:34:37 +01:00 committed by Andrew Morton
parent 8ac662f5da
commit faeec8e23c
1 changed files with 4 additions and 2 deletions
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6
mm/page_alloc.c
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@ -1238,13 +1238,15 @@ static void split_large_buddy(struct zone *zone, struct page *page,
if (order > pageblock_order)
order = pageblock_order;
while (pfn != end) {
do {
int mt = get_pfnblock_migratetype(page, pfn);
__free_one_page(page, pfn, zone, order, mt, fpi);
pfn += 1 << order;
if (pfn == end)
break;
page = pfn_to_page(pfn);
}
} while (1);
}
static void free_one_page(struct zone *zone, struct page *page,