From: Liu Shixin <liushixin2@xxxxxxxxxx> commit d1366e74342e75555af2648a2964deb2d5c92200 upstream. 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@xxxxxxxxxx Fixes: 3da0272a4c7d ("mm/compaction: correctly return failure with bogus compound_order in strict mode") Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx> Reviewed-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Nanyong Sun <sunnanyong@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/compaction.c +++ b/mm/compaction.c @@ -630,7 +630,8 @@ static unsigned long isolate_freepages_b if (PageCompound(page)) { const unsigned int order = compound_order(page); - if (blockpfn + (1UL << order) <= end_pfn) { + if ((order <= MAX_PAGE_ORDER) && + (blockpfn + (1UL << order) <= end_pfn)) { blockpfn += (1UL << order) - 1; page += (1UL << order) - 1; nr_scanned += (1UL << order) - 1; Patches currently in stable-queue which might be from liushixin2@xxxxxxxxxx are queue-6.12/mm-compaction-fix-ubsan-shift-out-of-bounds-warning.patch
