On 2025/1/23 10:10, Liu Shixin wrote:
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.
Fixes: 3da0272a4c7d ("mm/compaction: correctly return failure with bogus compound_order in strict mode")
Signed-off-by: Liu Shixin <liushixin2@xxxxxxxxxx>
---
LGTM. And I remember Vlastimil had the same concern before[1].
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
[1]
https://lore.kernel.org/all/6b055821-ce14-4a6d-959c-25ade4a9bfd7@xxxxxxx/
mm/compaction.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index a2b16b08cbbff..384e4672998e5 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -630,7 +630,8 @@ 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;
