As in 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.
Meanwhile,this patch also remove the check of EPERM on CAP_SYS_NICE.
The caller of migrate_pages should be able to migrate the target process
pages anywhere the caller can allocate memory, if the caller can access
the mm_struct.
Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Chris Salls <salls@xxxxxxxxxxx>
Cc: Christopher Lameter <cl@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Tan Xiaojun <tanxiaojun@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
---
v3:
* check whether node is empty after AND current task node, and then nodes
which have memory
v4:
* remove the check of EPERM on CAP_SYS_NICE.
Hi Vlastimil and Christopher,
Could you please help to review this version?
Thanks
Yisheng Xie
mm/mempolicy.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 65df28d..4da74b6 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1426,17 +1426,14 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
}
rcu_read_unlock();
- task_nodes = cpuset_mems_allowed(task);
- /* Is the user allowed to access the target nodes? */
- if (!nodes_subset(*new, task_nodes) && !capable(CAP_SYS_NICE)) {
- err = -EPERM;
+ task_nodes = cpuset_mems_allowed(current);
+ nodes_and(*new, *new, task_nodes);
+ if (nodes_empty(*new))
goto out_put;
- }
- if (!nodes_subset(*new, node_states[N_MEMORY])) {
- err = -EINVAL;
+ nodes_and(*new, *new, node_states[N_MEMORY]);
+ if (nodes_empty(*new))
goto out_put;
- }
err = security_task_movememory(task);
if (err)
--
1.7.12.4
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