hugetlb: fix race in alloc_fresh_huge_page()

That static `nid' index needs locking.  Without it we can end up calling
alloc_pages_node() with an illegal node ID and the kernel crashes.

Acked-by: gurudas pai <gurudas.pai@oracle.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index eaba7d6b25a01197dd10dc93c22a4ed1ef948db3..acc0fb3cf067125ce77b9821617c7ee39893c01e 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -101,13 +101,20 @@ static void free_huge_page(struct page *page)
 
 static int alloc_fresh_huge_page(void)
 {
-       static int nid = 0;
+       static int prev_nid;
        struct page *page;
-       page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
-                                       HUGETLB_PAGE_ORDER);
-       nid = next_node(nid, node_online_map);
+       static DEFINE_SPINLOCK(nid_lock);
+       int nid;
+
+       spin_lock(&nid_lock);
+       nid = next_node(prev_nid, node_online_map);
        if (nid == MAX_NUMNODES)
                nid = first_node(node_online_map);
+       prev_nid = nid;
+       spin_unlock(&nid_lock);
+
+       page = alloc_pages_node(nid, GFP_HIGHUSER|__GFP_COMP|__GFP_NOWARN,
+                                       HUGETLB_PAGE_ORDER);
        if (page) {
                set_compound_page_dtor(page, free_huge_page);
                spin_lock(&hugetlb_lock);