[Devel] [PATCH vz10] cgroup-v2: Validate controllers are enabled before hide/show

[Konstantin Khorenko]

Add validation to check that controllers are enabled in cgroup_ss_mask
before attempting to hide or show them. This prevents silent no-op
operations and returns -ENOENT error, consistent with the validation
logic in cgroup_subtree_control_write().

https://virtuozzo.atlassian.net/browse/VSTOR-119803
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
 kernel/cgroup/cgroup.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index f99f1672bde8c..5ab96088eee31 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4003,11 +4003,21 @@ static ssize_t cgroup_controllers_hidden_write(struct kernfs_open_file *of,
 				hide &= ~(1 << ssid);
 				continue;
 			}
+			/* Validate that controller is enabled in this cgroup */
+			if (!(cgroup_ss_mask(cgrp) & (1 << ssid))) {
+				ret = -ENOENT;
+				goto out_unlock;
+			}
 		} else if (show & (1 << ssid)) {
 			if (!(cgrp->hidden_ss_mask & (1 << ssid))) {
 				show &= ~(1 << ssid);
 				continue;
 			}
+			/* Validate that controller is enabled in this cgroup */
+			if (!(cgroup_ss_mask(cgrp) & (1 << ssid))) {
+				ret = -ENOENT;
+				goto out_unlock;
+			}
 		}
 	}
 
-- 
2.43.0