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
9
10 /* cgroup namespaces */
11
12 static struct ucounts *inc_cgroup_namespaces(struct user_namespace *ns)
13 {
14 return inc_ucount(ns, current_euid(), UCOUNT_CGROUP_NAMESPACES);
15 }
16
17 static void dec_cgroup_namespaces(struct ucounts *ucounts)
18 {
19 dec_ucount(ucounts, UCOUNT_CGROUP_NAMESPACES);
20 }
21
22 static struct cgroup_namespace *alloc_cgroup_ns(void)
23 {
24 struct cgroup_namespace *new_ns;
25 int ret;
26
27 new_ns = kzalloc(sizeof(struct cgroup_namespace), GFP_KERNEL_ACCOUNT);
28 if (!new_ns)
29 return ERR_PTR(-ENOMEM);
30 ret = ns_alloc_inum(&new_ns->ns);
31 if (ret) {
32 kfree(new_ns);
33 return ERR_PTR(ret);
34 }
35 refcount_set(&new_ns->ns.count, 1);
36 new_ns->ns.ops = &cgroupns_operations;
37 return new_ns;
38 }
39
40 void free_cgroup_ns(struct cgroup_namespace *ns)
41 {
42 put_css_set(ns->root_cset);
43 dec_cgroup_namespaces(ns->ucounts);
44 put_user_ns(ns->user_ns);
45 ns_free_inum(&ns->ns);
46 kfree(ns);
47 }
48 EXPORT_SYMBOL(free_cgroup_ns);
49
50 struct cgroup_namespace *copy_cgroup_ns(unsigned long flags,
51 struct user_namespace *user_ns,
52 struct cgroup_namespace *old_ns)
53 {
54 struct cgroup_namespace *new_ns;
55 struct ucounts *ucounts;
56 struct css_set *cset;
57
58 BUG_ON(!old_ns);
59
60 if (!(flags & CLONE_NEWCGROUP)) {
61 get_cgroup_ns(old_ns);
62 return old_ns;
63 }
64
65 /* Allow only sysadmin to create cgroup namespace. */
66 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
67 return ERR_PTR(-EPERM);
68
69 ucounts = inc_cgroup_namespaces(user_ns);
70 if (!ucounts)
71 return ERR_PTR(-ENOSPC);
72
73 /* It is not safe to take cgroup_mutex here */
74 spin_lock_irq(&css_set_lock);
75 cset = task_css_set(current);
76 get_css_set(cset);
77 spin_unlock_irq(&css_set_lock);
78
79 new_ns = alloc_cgroup_ns();
80 if (IS_ERR(new_ns)) {
81 put_css_set(cset);
82 dec_cgroup_namespaces(ucounts);
83 return new_ns;
84 }
85
86 new_ns->user_ns = get_user_ns(user_ns);
87 new_ns->ucounts = ucounts;
88 new_ns->root_cset = cset;
89
90 return new_ns;
91 }
92
93 static inline struct cgroup_namespace *to_cg_ns(struct ns_common *ns)
94 {
95 return container_of(ns, struct cgroup_namespace, ns);
96 }
97
98 static int cgroupns_install(struct nsset *nsset, struct ns_common *ns)
99 {
100 struct nsproxy *nsproxy = nsset->nsproxy;
101 struct cgroup_namespace *cgroup_ns = to_cg_ns(ns);
102
103 if (!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN) ||
104 !ns_capable(cgroup_ns->user_ns, CAP_SYS_ADMIN))
105 return -EPERM;
106
107 /* Don't need to do anything if we are attaching to our own cgroupns. */
108 if (cgroup_ns == nsproxy->cgroup_ns)
109 return 0;
110
111 get_cgroup_ns(cgroup_ns);
112 put_cgroup_ns(nsproxy->cgroup_ns);
113 nsproxy->cgroup_ns = cgroup_ns;
114
115 return 0;
116 }
117
118 static struct ns_common *cgroupns_get(struct task_struct *task)
119 {
120 struct cgroup_namespace *ns = NULL;
121 struct nsproxy *nsproxy;
122
123 task_lock(task);
124 nsproxy = task->nsproxy;
125 if (nsproxy) {
126 ns = nsproxy->cgroup_ns;
127 get_cgroup_ns(ns);
128 }
129 task_unlock(task);
130
131 return ns ? &ns->ns : NULL;
132 }
133
134 static void cgroupns_put(struct ns_common *ns)
135 {
136 put_cgroup_ns(to_cg_ns(ns));
137 }
138
139 static struct user_namespace *cgroupns_owner(struct ns_common *ns)
140 {
141 return to_cg_ns(ns)->user_ns;
142 }
143
144 const struct proc_ns_operations cgroupns_operations = {
145 .name = "cgroup",
146 .type = CLONE_NEWCGROUP,
147 .get = cgroupns_get,
148 .put = cgroupns_put,
149 .install = cgroupns_install,
150 .owner = cgroupns_owner,
151 };
152
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