1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/ipc/namespace.c
4 * Copyright (C) 2006 Pavel Emelyanov <xemul@openvz.org> OpenVZ, SWsoft Inc.
5 */
6
7 #include <linux/ipc.h>
8 #include <linux/msg.h>
9 #include <linux/ipc_namespace.h>
10 #include <linux/rcupdate.h>
11 #include <linux/nsproxy.h>
12 #include <linux/slab.h>
13 #include <linux/cred.h>
14 #include <linux/fs.h>
15 #include <linux/mount.h>
16 #include <linux/user_namespace.h>
17 #include <linux/proc_ns.h>
18 #include <linux/sched/task.h>
19
20 #include "util.h"
21
inc_ipc_namespaces(struct user_namespace * ns)22 static struct ucounts *inc_ipc_namespaces(struct user_namespace *ns)
23 {
24 return inc_ucount(ns, current_euid(), UCOUNT_IPC_NAMESPACES);
25 }
26
dec_ipc_namespaces(struct ucounts * ucounts)27 static void dec_ipc_namespaces(struct ucounts *ucounts)
28 {
29 dec_ucount(ucounts, UCOUNT_IPC_NAMESPACES);
30 }
31
create_ipc_ns(struct user_namespace * user_ns,struct ipc_namespace * old_ns)32 static struct ipc_namespace *create_ipc_ns(struct user_namespace *user_ns,
33 struct ipc_namespace *old_ns)
34 {
35 struct ipc_namespace *ns;
36 struct ucounts *ucounts;
37 int err;
38
39 err = -ENOSPC;
40 ucounts = inc_ipc_namespaces(user_ns);
41 if (!ucounts)
42 goto fail;
43
44 err = -ENOMEM;
45 ns = kmalloc(sizeof(struct ipc_namespace), GFP_KERNEL);
46 if (ns == NULL)
47 goto fail_dec;
48
49 err = ns_alloc_inum(&ns->ns);
50 if (err)
51 goto fail_free;
52 ns->ns.ops = &ipcns_operations;
53
54 refcount_set(&ns->count, 1);
55 ns->user_ns = get_user_ns(user_ns);
56 ns->ucounts = ucounts;
57
58 err = mq_init_ns(ns);
59 if (err)
60 goto fail_put;
61
62 sem_init_ns(ns);
63 msg_init_ns(ns);
64 shm_init_ns(ns);
65
66 return ns;
67
68 fail_put:
69 put_user_ns(ns->user_ns);
70 ns_free_inum(&ns->ns);
71 fail_free:
72 kfree(ns);
73 fail_dec:
74 dec_ipc_namespaces(ucounts);
75 fail:
76 return ERR_PTR(err);
77 }
78
copy_ipcs(unsigned long flags,struct user_namespace * user_ns,struct ipc_namespace * ns)79 struct ipc_namespace *copy_ipcs(unsigned long flags,
80 struct user_namespace *user_ns, struct ipc_namespace *ns)
81 {
82 if (!(flags & CLONE_NEWIPC))
83 return get_ipc_ns(ns);
84 return create_ipc_ns(user_ns, ns);
85 }
86
87 /*
88 * free_ipcs - free all ipcs of one type
89 * @ns: the namespace to remove the ipcs from
90 * @ids: the table of ipcs to free
91 * @free: the function called to free each individual ipc
92 *
93 * Called for each kind of ipc when an ipc_namespace exits.
94 */
free_ipcs(struct ipc_namespace * ns,struct ipc_ids * ids,void (* free)(struct ipc_namespace *,struct kern_ipc_perm *))95 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
96 void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
97 {
98 struct kern_ipc_perm *perm;
99 int next_id;
100 int total, in_use;
101
102 down_write(&ids->rwsem);
103
104 in_use = ids->in_use;
105
106 for (total = 0, next_id = 0; total < in_use; next_id++) {
107 perm = idr_find(&ids->ipcs_idr, next_id);
108 if (perm == NULL)
109 continue;
110 rcu_read_lock();
111 ipc_lock_object(perm);
112 free(ns, perm);
113 total++;
114 }
115 up_write(&ids->rwsem);
116 }
117
free_ipc_ns(struct ipc_namespace * ns)118 static void free_ipc_ns(struct ipc_namespace *ns)
119 {
120 sem_exit_ns(ns);
121 msg_exit_ns(ns);
122 shm_exit_ns(ns);
123
124 dec_ipc_namespaces(ns->ucounts);
125 put_user_ns(ns->user_ns);
126 ns_free_inum(&ns->ns);
127 kfree(ns);
128 }
129
130 /*
131 * put_ipc_ns - drop a reference to an ipc namespace.
132 * @ns: the namespace to put
133 *
134 * If this is the last task in the namespace exiting, and
135 * it is dropping the refcount to 0, then it can race with
136 * a task in another ipc namespace but in a mounts namespace
137 * which has this ipcns's mqueuefs mounted, doing some action
138 * with one of the mqueuefs files. That can raise the refcount.
139 * So dropping the refcount, and raising the refcount when
140 * accessing it through the VFS, are protected with mq_lock.
141 *
142 * (Clearly, a task raising the refcount on its own ipc_ns
143 * needn't take mq_lock since it can't race with the last task
144 * in the ipcns exiting).
145 */
put_ipc_ns(struct ipc_namespace * ns)146 void put_ipc_ns(struct ipc_namespace *ns)
147 {
148 if (refcount_dec_and_lock(&ns->count, &mq_lock)) {
149 mq_clear_sbinfo(ns);
150 spin_unlock(&mq_lock);
151 mq_put_mnt(ns);
152 free_ipc_ns(ns);
153 }
154 }
155
to_ipc_ns(struct ns_common * ns)156 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
157 {
158 return container_of(ns, struct ipc_namespace, ns);
159 }
160
ipcns_get(struct task_struct * task)161 static struct ns_common *ipcns_get(struct task_struct *task)
162 {
163 struct ipc_namespace *ns = NULL;
164 struct nsproxy *nsproxy;
165
166 task_lock(task);
167 nsproxy = task->nsproxy;
168 if (nsproxy)
169 ns = get_ipc_ns(nsproxy->ipc_ns);
170 task_unlock(task);
171
172 return ns ? &ns->ns : NULL;
173 }
174
ipcns_put(struct ns_common * ns)175 static void ipcns_put(struct ns_common *ns)
176 {
177 return put_ipc_ns(to_ipc_ns(ns));
178 }
179
ipcns_install(struct nsproxy * nsproxy,struct ns_common * new)180 static int ipcns_install(struct nsproxy *nsproxy, struct ns_common *new)
181 {
182 struct ipc_namespace *ns = to_ipc_ns(new);
183 if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
184 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
185 return -EPERM;
186
187 /* Ditch state from the old ipc namespace */
188 exit_sem(current);
189 put_ipc_ns(nsproxy->ipc_ns);
190 nsproxy->ipc_ns = get_ipc_ns(ns);
191 return 0;
192 }
193
ipcns_owner(struct ns_common * ns)194 static struct user_namespace *ipcns_owner(struct ns_common *ns)
195 {
196 return to_ipc_ns(ns)->user_ns;
197 }
198
199 const struct proc_ns_operations ipcns_operations = {
200 .name = "ipc",
201 .type = CLONE_NEWIPC,
202 .get = ipcns_get,
203 .put = ipcns_put,
204 .install = ipcns_install,
205 .owner = ipcns_owner,
206 };
207
