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144 lines · 3.2 KiB

1// SPDX-License-Identifier: GPL-2.0
2#include "cgroup-internal.h"
3
4#include <linux/sched/task.h>
5#include <linux/slab.h>
6#include <linux/nsproxy.h>
7#include <linux/proc_ns.h>
8#include <linux/nstree.h>
9
10/* cgroup namespaces */
11
12static struct ucounts *inc_cgroup_namespaces(struct user_namespace *ns)
13{
14 return inc_ucount(ns, current_euid(), UCOUNT_CGROUP_NAMESPACES);
15}
16
17static void dec_cgroup_namespaces(struct ucounts *ucounts)
18{
19 dec_ucount(ucounts, UCOUNT_CGROUP_NAMESPACES);
20}
21
22static struct cgroup_namespace *alloc_cgroup_ns(void)
23{
24 struct cgroup_namespace *new_ns __free(kfree) = NULL;
25 int ret;
26
27 new_ns = kzalloc_obj(struct cgroup_namespace, GFP_KERNEL_ACCOUNT);
28 if (!new_ns)
29 return ERR_PTR(-ENOMEM);
30 ret = ns_common_init(new_ns);
31 if (ret)
32 return ERR_PTR(ret);
33 return no_free_ptr(new_ns);
34}
35
36void free_cgroup_ns(struct cgroup_namespace *ns)
37{
38 ns_tree_remove(ns);
39 put_css_set(ns->root_cset);
40 dec_cgroup_namespaces(ns->ucounts);
41 put_user_ns(ns->user_ns);
42 ns_common_free(ns);
43 /* Concurrent nstree traversal depends on a grace period. */
44 kfree_rcu(ns, ns.ns_rcu);
45}
46EXPORT_SYMBOL(free_cgroup_ns);
47
48struct cgroup_namespace *copy_cgroup_ns(u64 flags,
49 struct user_namespace *user_ns,
50 struct cgroup_namespace *old_ns)
51{
52 struct cgroup_namespace *new_ns;
53 struct ucounts *ucounts;
54 struct css_set *cset;
55
56 BUG_ON(!old_ns);
57
58 if (!(flags & CLONE_NEWCGROUP)) {
59 get_cgroup_ns(old_ns);
60 return old_ns;
61 }
62
63 /* Allow only sysadmin to create cgroup namespace. */
64 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
65 return ERR_PTR(-EPERM);
66
67 ucounts = inc_cgroup_namespaces(user_ns);
68 if (!ucounts)
69 return ERR_PTR(-ENOSPC);
70
71 /* It is not safe to take cgroup_mutex here */
72 spin_lock_irq(&css_set_lock);
73 cset = task_css_set(current);
74 get_css_set(cset);
75 spin_unlock_irq(&css_set_lock);
76
77 new_ns = alloc_cgroup_ns();
78 if (IS_ERR(new_ns)) {
79 put_css_set(cset);
80 dec_cgroup_namespaces(ucounts);
81 return new_ns;
82 }
83
84 new_ns->user_ns = get_user_ns(user_ns);
85 new_ns->ucounts = ucounts;
86 new_ns->root_cset = cset;
87
88 ns_tree_add(new_ns);
89 return new_ns;
90}
91
92static int cgroupns_install(struct nsset *nsset, struct ns_common *ns)
93{
94 struct nsproxy *nsproxy = nsset->nsproxy;
95 struct cgroup_namespace *cgroup_ns = to_cg_ns(ns);
96
97 if (!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN) ||
98 !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
99 return -EPERM;
100
101 /* Don't need to do anything if we are attaching to our own cgroupns. */
102 if (cgroup_ns == nsproxy->cgroup_ns)
103 return 0;
104
105 get_cgroup_ns(cgroup_ns);
106 put_cgroup_ns(nsproxy->cgroup_ns);
107 nsproxy->cgroup_ns = cgroup_ns;
108
109 return 0;
110}
111
112static struct ns_common *cgroupns_get(struct task_struct *task)
113{
114 struct cgroup_namespace *ns = NULL;
115 struct nsproxy *nsproxy;
116
117 task_lock(task);
118 nsproxy = task->nsproxy;
119 if (nsproxy) {
120 ns = nsproxy->cgroup_ns;
121 get_cgroup_ns(ns);
122 }
123 task_unlock(task);
124
125 return ns ? &ns->ns : NULL;
126}
127
128static void cgroupns_put(struct ns_common *ns)
129{
130 put_cgroup_ns(to_cg_ns(ns));
131}
132
133static struct user_namespace *cgroupns_owner(struct ns_common *ns)
134{
135 return to_cg_ns(ns)->user_ns;
136}
137
138const struct proc_ns_operations cgroupns_operations = {
139 .name = "cgroup",
140 .get = cgroupns_get,
141 .put = cgroupns_put,
142 .install = cgroupns_install,
143 .owner = cgroupns_owner,
144};