858d72ead4
When a task enters a new namespace via a clone() or unshare(), a new cgroup is created and the task moves into it. This version names cgroups which are automatically created using cgroup_clone() as "node_<pid>" where pid is the pid of the unsharing or cloned process. (Thanks Pavel for the idea) This is safe because if the process unshares again, it will create /cgroups/(...)/node_<pid>/node_<pid> The only possibilities (AFAICT) for a -EEXIST on unshare are 1. pid wraparound 2. a process fails an unshare, then tries again. Case 1 is unlikely enough that I ignore it (at least for now). In case 2, the node_<pid> will be empty and can be rmdir'ed to make the subsequent unshare() succeed. Changelog: Name cloned cgroups as "node_<pid>". [clg@fr.ibm.com: fix order of cgroup subsystems in init/Kconfig] Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> Cc: Paul Menage <menage@google.com> Signed-off-by: Cedric Le Goater <clg@fr.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
100 lines
2.2 KiB
C
100 lines
2.2 KiB
C
/*
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* ns_cgroup.c - namespace cgroup subsystem
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*
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* Copyright 2006, 2007 IBM Corp
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*/
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#include <linux/module.h>
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#include <linux/cgroup.h>
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#include <linux/fs.h>
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struct ns_cgroup {
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struct cgroup_subsys_state css;
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spinlock_t lock;
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};
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struct cgroup_subsys ns_subsys;
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static inline struct ns_cgroup *cgroup_to_ns(
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struct cgroup *cgroup)
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{
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return container_of(cgroup_subsys_state(cgroup, ns_subsys_id),
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struct ns_cgroup, css);
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}
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int ns_cgroup_clone(struct task_struct *task)
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{
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return cgroup_clone(task, &ns_subsys);
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}
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/*
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* Rules:
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* 1. you can only enter a cgroup which is a child of your current
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* cgroup
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* 2. you can only place another process into a cgroup if
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* a. you have CAP_SYS_ADMIN
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* b. your cgroup is an ancestor of task's destination cgroup
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* (hence either you are in the same cgroup as task, or in an
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* ancestor cgroup thereof)
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*/
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static int ns_can_attach(struct cgroup_subsys *ss,
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struct cgroup *new_cgroup, struct task_struct *task)
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{
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struct cgroup *orig;
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if (current != task) {
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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if (!cgroup_is_descendant(new_cgroup))
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return -EPERM;
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}
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if (atomic_read(&new_cgroup->count) != 0)
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return -EPERM;
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orig = task_cgroup(task, ns_subsys_id);
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if (orig && orig != new_cgroup->parent)
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return -EPERM;
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return 0;
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}
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/*
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* Rules: you can only create a cgroup if
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* 1. you are capable(CAP_SYS_ADMIN)
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* 2. the target cgroup is a descendant of your own cgroup
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*/
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static struct cgroup_subsys_state *ns_create(struct cgroup_subsys *ss,
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struct cgroup *cgroup)
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{
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struct ns_cgroup *ns_cgroup;
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if (!capable(CAP_SYS_ADMIN))
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return ERR_PTR(-EPERM);
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if (!cgroup_is_descendant(cgroup))
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return ERR_PTR(-EPERM);
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ns_cgroup = kzalloc(sizeof(*ns_cgroup), GFP_KERNEL);
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if (!ns_cgroup)
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return ERR_PTR(-ENOMEM);
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spin_lock_init(&ns_cgroup->lock);
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return &ns_cgroup->css;
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}
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static void ns_destroy(struct cgroup_subsys *ss,
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struct cgroup *cgroup)
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{
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struct ns_cgroup *ns_cgroup;
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ns_cgroup = cgroup_to_ns(cgroup);
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kfree(ns_cgroup);
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}
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struct cgroup_subsys ns_subsys = {
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.name = "ns",
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.can_attach = ns_can_attach,
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.create = ns_create,
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.destroy = ns_destroy,
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.subsys_id = ns_subsys_id,
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};
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