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 = kzalloc(sizeof(struct ipc_namespace), GFP_KERNEL_ACCOUNT);
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->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 	err = -ENOMEM;
63 	if (!setup_mq_sysctls(ns))
64 		goto fail_put;
65 
66 	if (!setup_ipc_sysctls(ns))
67 		goto fail_mq;
68 
69 	err = msg_init_ns(ns);
70 	if (err)
71 		goto fail_put;
72 
73 	sem_init_ns(ns);
74 	shm_init_ns(ns);
75 
76 	return ns;
77 
78 fail_mq:
79 	retire_mq_sysctls(ns);
80 
81 fail_put:
82 	put_user_ns(ns->user_ns);
83 	ns_free_inum(&ns->ns);
84 fail_free:
85 	kfree(ns);
86 fail_dec:
87 	dec_ipc_namespaces(ucounts);
88 fail:
89 	return ERR_PTR(err);
90 }
91 
copy_ipcs(unsigned long flags,struct user_namespace * user_ns,struct ipc_namespace * ns)92 struct ipc_namespace *copy_ipcs(unsigned long flags,
93 	struct user_namespace *user_ns, struct ipc_namespace *ns)
94 {
95 	if (!(flags & CLONE_NEWIPC))
96 		return get_ipc_ns(ns);
97 	return create_ipc_ns(user_ns, ns);
98 }
99 
100 /*
101  * free_ipcs - free all ipcs of one type
102  * @ns:   the namespace to remove the ipcs from
103  * @ids:  the table of ipcs to free
104  * @free: the function called to free each individual ipc
105  *
106  * Called for each kind of ipc when an ipc_namespace exits.
107  */
free_ipcs(struct ipc_namespace * ns,struct ipc_ids * ids,void (* free)(struct ipc_namespace *,struct kern_ipc_perm *))108 void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
109 	       void (*free)(struct ipc_namespace *, struct kern_ipc_perm *))
110 {
111 	struct kern_ipc_perm *perm;
112 	int next_id;
113 	int total, in_use;
114 
115 	down_write(&ids->rwsem);
116 
117 	in_use = ids->in_use;
118 
119 	for (total = 0, next_id = 0; total < in_use; next_id++) {
120 		perm = idr_find(&ids->ipcs_idr, next_id);
121 		if (perm == NULL)
122 			continue;
123 		rcu_read_lock();
124 		ipc_lock_object(perm);
125 		free(ns, perm);
126 		total++;
127 	}
128 	up_write(&ids->rwsem);
129 }
130 
free_ipc_ns(struct ipc_namespace * ns)131 static void free_ipc_ns(struct ipc_namespace *ns)
132 {
133 	/* mq_put_mnt() waits for a grace period as kern_unmount()
134 	 * uses synchronize_rcu().
135 	 */
136 	mq_put_mnt(ns);
137 	sem_exit_ns(ns);
138 	msg_exit_ns(ns);
139 	shm_exit_ns(ns);
140 
141 	retire_mq_sysctls(ns);
142 	retire_ipc_sysctls(ns);
143 
144 	dec_ipc_namespaces(ns->ucounts);
145 	put_user_ns(ns->user_ns);
146 	ns_free_inum(&ns->ns);
147 	kfree(ns);
148 }
149 
150 static LLIST_HEAD(free_ipc_list);
free_ipc(struct work_struct * unused)151 static void free_ipc(struct work_struct *unused)
152 {
153 	struct llist_node *node = llist_del_all(&free_ipc_list);
154 	struct ipc_namespace *n, *t;
155 
156 	llist_for_each_entry_safe(n, t, node, mnt_llist)
157 		free_ipc_ns(n);
158 }
159 
160 /*
161  * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
162  */
163 static DECLARE_WORK(free_ipc_work, free_ipc);
164 
165 /*
166  * put_ipc_ns - drop a reference to an ipc namespace.
167  * @ns: the namespace to put
168  *
169  * If this is the last task in the namespace exiting, and
170  * it is dropping the refcount to 0, then it can race with
171  * a task in another ipc namespace but in a mounts namespace
172  * which has this ipcns's mqueuefs mounted, doing some action
173  * with one of the mqueuefs files.  That can raise the refcount.
174  * So dropping the refcount, and raising the refcount when
175  * accessing it through the VFS, are protected with mq_lock.
176  *
177  * (Clearly, a task raising the refcount on its own ipc_ns
178  * needn't take mq_lock since it can't race with the last task
179  * in the ipcns exiting).
180  */
put_ipc_ns(struct ipc_namespace * ns)181 void put_ipc_ns(struct ipc_namespace *ns)
182 {
183 	if (refcount_dec_and_lock(&ns->ns.count, &mq_lock)) {
184 		mq_clear_sbinfo(ns);
185 		spin_unlock(&mq_lock);
186 
187 		if (llist_add(&ns->mnt_llist, &free_ipc_list))
188 			schedule_work(&free_ipc_work);
189 	}
190 }
191 
to_ipc_ns(struct ns_common * ns)192 static inline struct ipc_namespace *to_ipc_ns(struct ns_common *ns)
193 {
194 	return container_of(ns, struct ipc_namespace, ns);
195 }
196 
ipcns_get(struct task_struct * task)197 static struct ns_common *ipcns_get(struct task_struct *task)
198 {
199 	struct ipc_namespace *ns = NULL;
200 	struct nsproxy *nsproxy;
201 
202 	task_lock(task);
203 	nsproxy = task->nsproxy;
204 	if (nsproxy)
205 		ns = get_ipc_ns(nsproxy->ipc_ns);
206 	task_unlock(task);
207 
208 	return ns ? &ns->ns : NULL;
209 }
210 
ipcns_put(struct ns_common * ns)211 static void ipcns_put(struct ns_common *ns)
212 {
213 	return put_ipc_ns(to_ipc_ns(ns));
214 }
215 
ipcns_install(struct nsset * nsset,struct ns_common * new)216 static int ipcns_install(struct nsset *nsset, struct ns_common *new)
217 {
218 	struct nsproxy *nsproxy = nsset->nsproxy;
219 	struct ipc_namespace *ns = to_ipc_ns(new);
220 	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN) ||
221 	    !ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN))
222 		return -EPERM;
223 
224 	put_ipc_ns(nsproxy->ipc_ns);
225 	nsproxy->ipc_ns = get_ipc_ns(ns);
226 	return 0;
227 }
228 
ipcns_owner(struct ns_common * ns)229 static struct user_namespace *ipcns_owner(struct ns_common *ns)
230 {
231 	return to_ipc_ns(ns)->user_ns;
232 }
233 
234 const struct proc_ns_operations ipcns_operations = {
235 	.name		= "ipc",
236 	.type		= CLONE_NEWIPC,
237 	.get		= ipcns_get,
238 	.put		= ipcns_put,
239 	.install	= ipcns_install,
240 	.owner		= ipcns_owner,
241 };
242