On Tue, Mar 29, 2016 at 02:25:03PM +0200, Vlastimil Babka wrote:

On 03/25/2016 07:56 AM, Xishi Qiu wrote:

quoted

It is incorrect to use next_node to find a target node, it will
return MAX_NUMNODES or invalid node. This will lead to crash in
buddy system allocation.

One possible place of crash is:
alloc_huge_page_node()
    dequeue_huge_page_node()
        [accesses h->hugepage_freelists[nid] with size MAX_NUMANODES]

quoted

Signed-off-by: Xishi Qiu <redacted>

Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle
hugepage")
Cc: stable
Acked-by: Vlastimil Babka <redacted>

Thanks everyone for finding/fixing the bug!

Acked-by: Naoya Horiguchi <redacted>

quoted

---
 mm/page_isolation.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 92c4c36..31555b6 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c

@@ -289,11 +289,11 @@ struct page *alloc_migrate_target(struct page *page, unsigned long private,
 	 * now as a simple work-around, we use the next node for destination.
 	 */
 	if (PageHuge(page)) {
-		nodemask_t src = nodemask_of_node(page_to_nid(page));
-		nodemask_t dst;
-		nodes_complement(dst, src);
+		int node = next_online_node(page_to_nid(page));
+		if (node == MAX_NUMNODES)
+			node = first_online_node;
 		return alloc_huge_page_node(page_hstate(compound_head(page)),
-					    next_node(page_to_nid(page), dst));
+					    node);
 	}

 	if (PageHighMem(page))

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