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| author | David Hildenbrand <david@redhat.com> | 2024-12-10 10:34:37 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-12-18 19:04:45 -0800 |
| commit | faeec8e23c10bd30e8aa759a2eb3018dae00f924 (patch) | |
| tree | df0e8a66c887a19e7258e946a57ed42bf8d3430c | |
| parent | 8ac662f5da19f5873fdd94c48a5cdb45b2e1b58f (diff) | |
| download | lwn-faeec8e23c10bd30e8aa759a2eb3018dae00f924.tar.gz lwn-faeec8e23c10bd30e8aa759a2eb3018dae00f924.zip | |
mm/page_alloc: don't call pfn_to_page() on possibly non-existent PFN in split_large_buddy()
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: fd919a85cd55 ("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>
| -rw-r--r-- | mm/page_alloc.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1cb4b8c8886d..cae7b93864c2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -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, |