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: 3da0272a4c7d ("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>

diff --git a/mm/compaction.c b/mm/compaction.c
index 07bd22789f07c48acaa4a59742869d4187a0d0d1..0f49f060d251ea76cbc7628e3dd4b05d18a0e28d 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -631,7 +631,8 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
                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;