[PATCH v3 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

[Yisheng Xie]

As manpage of migrate_pages, the errno should be set to EINVAL when
none of the node IDs specified by new_nodes are on-line and allowed
by the process's current cpuset context, or none of the specified
nodes contain memory. However, when test by following case:

	new_nodes = 0;
	old_nodes = 0xf;
	ret = migrate_pages(pid, old_nodes, new_nodes, MAX);

The ret will be 0 and no errno is set. As the new_nodes is empty,
we should expect EINVAL as documented.

To fix the case like above, this patch check whether target nodes
AND current task_nodes is empty, and then check whether AND
node_states[N_MEMORY] is empty.

Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx>
---
 mm/mempolicy.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 65df28d..f604b22 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1433,10 +1433,14 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
 		goto out_put;
 	}
 
-	if (!nodes_subset(*new, node_states[N_MEMORY])) {
-		err = -EINVAL;
+	task_nodes = cpuset_mems_allowed(current);
+	nodes_and(*new, *new, task_nodes);
+	if (nodes_empty(*new))
+		goto out_put;
+
+	nodes_and(*new, *new, node_states[N_MEMORY]);
+	if (nodes_empty(*new))
 		goto out_put;
-	}
 
 	err = security_task_movememory(task);
 	if (err)
-- 
1.8.3.1