Commit d1366e74 authored by Liu Shixin's avatar Liu Shixin Committed by Andrew Morton
Browse files

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: 3da0272a ("mm/compaction: correctly return failure with bogus compound_order in strict mode")
Signed-off-by: default avatarLiu Shixin <liushixin2@huawei.com>
Reviewed-by: default avatarKemeng Shi <shikemeng@huaweicloud.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarOscar 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 502269ab

mm/compaction.c

+2 −1
Original line number Diff line number Diff line
@@ -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;