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Liu Shixinakpm00
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mm/compaction: fix UBSAN shift-out-of-bounds warning
syzkaller reported a UBSAN shift-out-of-bounds warning of (1UL << order) in isolate_freepages_block(). The bogus compound_order can be any value because it is union with flags. Add back the MAX_PAGE_ORDER check to fix the warning. Link: https://lkml.kernel.org/r/20250123021029.2826736-1-liushixin2@huawei.com Fixes: 3da0272 ("mm/compaction: correctly return failure with bogus compound_order in strict mode") Signed-off-by: Liu Shixin <liushixin2@huawei.com> Reviewed-by: Kemeng Shi <shikemeng@huaweicloud.com> Acked-by: David Hildenbrand <david@redhat.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: David Hildenbrand <david@redhat.com> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Nanyong Sun <sunnanyong@huawei.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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mm/compaction.c

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -631,7 +631,8 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
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if (PageCompound(page)) {
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const unsigned int order = compound_order(page);
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if (blockpfn + (1UL << order) <= end_pfn) {
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if ((order <= MAX_PAGE_ORDER) &&
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(blockpfn + (1UL << order) <= end_pfn)) {
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blockpfn += (1UL << order) - 1;
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page += (1UL << order) - 1;
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nr_scanned += (1UL << order) - 1;

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