path: root/Documentation
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authorColin Cross <>2011-07-12 19:53:24 -0700
committerDan Willemsen <>2011-11-30 21:38:49 -0800
commita237ee7830a0445a27af7fd24bdc3414b9553d35 (patch)
treec0c9be8c1f24e09a673643426db50c193791e838 /Documentation
parentf971f6c015d74c9653a15fa1357144ead2ff7e7e (diff)
cgroup: Add generic cgroup subsystem permission checks
Rather than using explicit euid == 0 checks when trying to move tasks into a cgroup via CFS, move permission checks into each specific cgroup subsystem. If a subsystem does not specify a 'allow_attach' handler, then we fall back to doing our checks the old way. Use the 'allow_attach' handler for the 'cpu' cgroup to allow non-root processes to add arbitrary processes to a 'cpu' cgroup if it has the CAP_SYS_NICE capability set. This version of the patch adds a 'allow_attach' handler instead of reusing the 'can_attach' handler. If the 'can_attach' handler is reused, a new cgroup that implements 'can_attach' but not the permission checks could end up with no permission checks at all. Change-Id: Icfa950aa9321d1ceba362061d32dc7dfa2c64f0c Original-Author: San Mehat <> Signed-off-by: Colin Cross <>
Diffstat (limited to 'Documentation')
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index cd67e90003c0..60d82e1e498d 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -593,6 +593,15 @@ there are not tasks in the cgroup. If pre_destroy() returns error code,
rmdir() will fail with it. From this behavior, pre_destroy() can be
called multiple times against a cgroup.
+int allow_attach(struct cgroup *cgrp, struct task_struct *task)
+(cgroup_mutex held by caller)
+Called prior to moving a task into a cgroup; if the subsystem
+returns an error, this will abort the attach operation. Used
+to extend the permission checks - if all subsystems in a cgroup
+return 0, the attach will be allowed to proceed, even if the
+default permission check (root or same user) fails.
int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task)
(cgroup_mutex held by caller)