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From: Grzegorz Nosek <r...@localdomain.pl>
The ns_proxy cgroup allows moving processes to child cgroups only one
level deep at a time. This commit relaxes this restriction and makes it
possible to attach tasks directly to grandchild cgroups, e.g.:
($pid is in the root cgroup)
echo $pid > /cgroup/CG1/CG2/tasks
Previously this operation would fail with -EPERM and would have to be
performed as two steps:
echo $pid > /cgroup/CG1/tasks
echo $pid > /cgroup/CG1/CG2/tasks
Signed-off-by: Grzegorz Nosek <r...@localdomain.pl>
Reviewed-by: Li Zefan <l...@cn.fujitsu.com>
Cc: Paul Menage <men...@google.com>
Cc: Balbir Singh <bal...@in.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
Cc: Pavel Emelyanov <xe...@openvz.org>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
---
include/linux/cgroup.h | 4 ++--
kernel/cgroup.c | 12 +++++++-----
kernel/ns_cgroup.c | 9 +++------
3 files changed, 12 insertions(+), 13 deletions(-)
diff -puN
include/linux/cgroup.h~relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups
include/linux/cgroup.h
---
a/include/linux/cgroup.h~relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups
+++ a/include/linux/cgroup.h
@@ -344,8 +344,8 @@ int cgroup_path(const struct cgroup *cgr
int cgroup_task_count(const struct cgroup *cgrp);
-/* Return true if the cgroup is a descendant of the current cgroup */
-int cgroup_is_descendant(const struct cgroup *cgrp);
+/* Return true if cgrp is a descendant of the task's cgroup */
+int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
/* Control Group subsystem type. See Documentation/cgroups.txt for details */
diff -puN
kernel/cgroup.c~relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups
kernel/cgroup.c
---
a/kernel/cgroup.c~relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups
+++ a/kernel/cgroup.c
@@ -3072,18 +3072,19 @@ int cgroup_clone(struct task_struct *tsk
}
/**
- * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp
+ * cgroup_is_descendant - see if @cgrp is a descendant of @task's cgrp
* @cgrp: the cgroup in question
+ * @task: the task in question
*
- * See if @cgrp is a descendant of the current task's cgroup in
- * the appropriate hierarchy.
+ * See if @cgrp is a descendant of @task's cgroup in the appropriate
+ * hierarchy.
*
* If we are sending in dummytop, then presumably we are creating
* the top cgroup in the subsystem.
*
* Called only by the ns (nsproxy) cgroup.
*/
-int cgroup_is_descendant(const struct cgroup *cgrp)
+int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task)
{
int ret;
struct cgroup *target;
@@ -3093,7 +3094,8 @@ int cgroup_is_descendant(const struct cg
return 1;
get_first_subsys(cgrp, NULL, &subsys_id);
- target = task_cgroup(current, subsys_id);
+ target = task_cgroup(task, subsys_id);
+
while (cgrp != target && cgrp!= cgrp->top_cgroup)
cgrp = cgrp->parent;
ret = (cgrp == target);
diff -puN
kernel/ns_cgroup.c~relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups
kernel/ns_cgroup.c
---
a/kernel/ns_cgroup.c~relax-ns_can_attach-checks-to-allow-attaching-to-grandchild-cgroups
+++ a/kernel/ns_cgroup.c
@@ -45,21 +45,18 @@ int ns_cgroup_clone(struct task_struct *
static int ns_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup, struct task_struct *task)
{
- struct cgroup *orig;
-
if (current != task) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
- if (!cgroup_is_descendant(new_cgroup))
+ if (!cgroup_is_descendant(new_cgroup, current))
return -EPERM;
}
if (atomic_read(&new_cgroup->count) != 0)
return -EPERM;
- orig = task_cgroup(task, ns_subsys_id);
- if (orig && orig != new_cgroup->parent)
+ if (!cgroup_is_descendant(new_cgroup, task))
return -EPERM;
return 0;
@@ -77,7 +74,7 @@ static struct cgroup_subsys_state *ns_cr
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
- if (!cgroup_is_descendant(cgroup))
+ if (!cgroup_is_descendant(cgroup, current))
return ERR_PTR(-EPERM);
ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
_
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