[PATCH] mm/hugetlb: Guard dequeue_hugetlb_folio_nodemask against NUMA_NO_NODE uses

[Oscar Salvador <osalvador@suse.de>]

dequeue_hugetlb_folio_nodemask() expects a preferred node where to get the
hugetlb page from.
It does not expect, though, users to pass NUMA_NO_NODE, otherwise we will
get trash when trying to get the zonelist from that node.
All current users are careful enough to not pass NUMA_NO_NODE, but
it opens the door for new users to get this wrong since it is not
documented [0].
Guard against this by getting the local nid if NUMA_NO_NODE was passed.

[0] https://lore.kernel.org/linux-mm/0000000000004f12bb061a9acf07@google.com/

Closes: https://lore.kernel.org/linux-mm/0000000000004f12bb061a9acf07@google.com/
Reported-and-tested-by: syzbot+569ed13f4054f271087b@syzkaller.appspotmail.com
Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/hugetlb.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3518321f6598..6a5ea898e4da 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1355,6 +1355,10 @@ static struct folio *dequeue_hugetlb_folio_nodemask(struct hstate *h, gfp_t gfp_
 	struct zoneref *z;
 	int node = NUMA_NO_NODE;
 
+	/* 'nid' should not be NUMA_NO_NODE. Try to catch any misuse of it and rectifiy. */
+	if (nid == NUMA_NO_NODE)
+		nid = numa_node_id();
+
 	zonelist = node_zonelist(nid, gfp_mask);
 
 retry_cpuset:
-- 
2.45.2