1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/mount.h>
3 #include <linux/pseudo_fs.h>
4 #include <linux/file.h>
5 #include <linux/fs.h>
6 #include <linux/proc_fs.h>
7 #include <linux/proc_ns.h>
8 #include <linux/magic.h>
9 #include <linux/ktime.h>
10 #include <linux/seq_file.h>
11 #include <linux/user_namespace.h>
12 #include <linux/nsfs.h>
13 #include <linux/uaccess.h>
14
15 #include "internal.h"
16
17 static struct vfsmount *nsfs_mnt;
18
19 static long ns_ioctl(struct file *filp, unsigned int ioctl,
20 unsigned long arg);
21 static const struct file_operations ns_file_operations = {
22 .llseek = no_llseek,
23 .unlocked_ioctl = ns_ioctl,
24 .compat_ioctl = compat_ptr_ioctl,
25 };
26
ns_dname(struct dentry * dentry,char * buffer,int buflen)27 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
28 {
29 struct inode *inode = d_inode(dentry);
30 struct ns_common *ns = inode->i_private;
31 const struct proc_ns_operations *ns_ops = ns->ops;
32
33 return dynamic_dname(buffer, buflen, "%s:[%lu]",
34 ns_ops->name, inode->i_ino);
35 }
36
37 const struct dentry_operations ns_dentry_operations = {
38 .d_delete = always_delete_dentry,
39 .d_dname = ns_dname,
40 .d_prune = stashed_dentry_prune,
41 };
42
nsfs_evict(struct inode * inode)43 static void nsfs_evict(struct inode *inode)
44 {
45 struct ns_common *ns = inode->i_private;
46 clear_inode(inode);
47 ns->ops->put(ns);
48 }
49
ns_get_path_cb(struct path * path,ns_get_path_helper_t * ns_get_cb,void * private_data)50 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
51 void *private_data)
52 {
53 struct ns_common *ns;
54
55 ns = ns_get_cb(private_data);
56 if (!ns)
57 return -ENOENT;
58
59 return path_from_stashed(&ns->stashed, nsfs_mnt, ns, path);
60 }
61
62 struct ns_get_path_task_args {
63 const struct proc_ns_operations *ns_ops;
64 struct task_struct *task;
65 };
66
ns_get_path_task(void * private_data)67 static struct ns_common *ns_get_path_task(void *private_data)
68 {
69 struct ns_get_path_task_args *args = private_data;
70
71 return args->ns_ops->get(args->task);
72 }
73
ns_get_path(struct path * path,struct task_struct * task,const struct proc_ns_operations * ns_ops)74 int ns_get_path(struct path *path, struct task_struct *task,
75 const struct proc_ns_operations *ns_ops)
76 {
77 struct ns_get_path_task_args args = {
78 .ns_ops = ns_ops,
79 .task = task,
80 };
81
82 return ns_get_path_cb(path, ns_get_path_task, &args);
83 }
84
open_related_ns(struct ns_common * ns,struct ns_common * (* get_ns)(struct ns_common * ns))85 int open_related_ns(struct ns_common *ns,
86 struct ns_common *(*get_ns)(struct ns_common *ns))
87 {
88 struct path path = {};
89 struct ns_common *relative;
90 struct file *f;
91 int err;
92 int fd;
93
94 fd = get_unused_fd_flags(O_CLOEXEC);
95 if (fd < 0)
96 return fd;
97
98 relative = get_ns(ns);
99 if (IS_ERR(relative)) {
100 put_unused_fd(fd);
101 return PTR_ERR(relative);
102 }
103
104 err = path_from_stashed(&relative->stashed, nsfs_mnt, relative, &path);
105 if (err < 0) {
106 put_unused_fd(fd);
107 return err;
108 }
109
110 f = dentry_open(&path, O_RDONLY, current_cred());
111 path_put(&path);
112 if (IS_ERR(f)) {
113 put_unused_fd(fd);
114 fd = PTR_ERR(f);
115 } else
116 fd_install(fd, f);
117
118 return fd;
119 }
120 EXPORT_SYMBOL_GPL(open_related_ns);
121
ns_ioctl(struct file * filp,unsigned int ioctl,unsigned long arg)122 static long ns_ioctl(struct file *filp, unsigned int ioctl,
123 unsigned long arg)
124 {
125 struct user_namespace *user_ns;
126 struct ns_common *ns = get_proc_ns(file_inode(filp));
127 uid_t __user *argp;
128 uid_t uid;
129
130 switch (ioctl) {
131 case NS_GET_USERNS:
132 return open_related_ns(ns, ns_get_owner);
133 case NS_GET_PARENT:
134 if (!ns->ops->get_parent)
135 return -EINVAL;
136 return open_related_ns(ns, ns->ops->get_parent);
137 case NS_GET_NSTYPE:
138 return ns->ops->type;
139 case NS_GET_OWNER_UID:
140 if (ns->ops->type != CLONE_NEWUSER)
141 return -EINVAL;
142 user_ns = container_of(ns, struct user_namespace, ns);
143 argp = (uid_t __user *) arg;
144 uid = from_kuid_munged(current_user_ns(), user_ns->owner);
145 return put_user(uid, argp);
146 default:
147 return -ENOTTY;
148 }
149 }
150
ns_get_name(char * buf,size_t size,struct task_struct * task,const struct proc_ns_operations * ns_ops)151 int ns_get_name(char *buf, size_t size, struct task_struct *task,
152 const struct proc_ns_operations *ns_ops)
153 {
154 struct ns_common *ns;
155 int res = -ENOENT;
156 const char *name;
157 ns = ns_ops->get(task);
158 if (ns) {
159 name = ns_ops->real_ns_name ? : ns_ops->name;
160 res = snprintf(buf, size, "%s:[%u]", name, ns->inum);
161 ns_ops->put(ns);
162 }
163 return res;
164 }
165
proc_ns_file(const struct file * file)166 bool proc_ns_file(const struct file *file)
167 {
168 return file->f_op == &ns_file_operations;
169 }
170
171 /**
172 * ns_match() - Returns true if current namespace matches dev/ino provided.
173 * @ns: current namespace
174 * @dev: dev_t from nsfs that will be matched against current nsfs
175 * @ino: ino_t from nsfs that will be matched against current nsfs
176 *
177 * Return: true if dev and ino matches the current nsfs.
178 */
ns_match(const struct ns_common * ns,dev_t dev,ino_t ino)179 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino)
180 {
181 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev);
182 }
183
184
nsfs_show_path(struct seq_file * seq,struct dentry * dentry)185 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
186 {
187 struct inode *inode = d_inode(dentry);
188 const struct ns_common *ns = inode->i_private;
189 const struct proc_ns_operations *ns_ops = ns->ops;
190
191 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
192 return 0;
193 }
194
195 static const struct super_operations nsfs_ops = {
196 .statfs = simple_statfs,
197 .evict_inode = nsfs_evict,
198 .show_path = nsfs_show_path,
199 };
200
nsfs_init_inode(struct inode * inode,void * data)201 static int nsfs_init_inode(struct inode *inode, void *data)
202 {
203 struct ns_common *ns = data;
204
205 inode->i_private = data;
206 inode->i_mode |= S_IRUGO;
207 inode->i_fop = &ns_file_operations;
208 inode->i_ino = ns->inum;
209 return 0;
210 }
211
nsfs_put_data(void * data)212 static void nsfs_put_data(void *data)
213 {
214 struct ns_common *ns = data;
215 ns->ops->put(ns);
216 }
217
218 static const struct stashed_operations nsfs_stashed_ops = {
219 .init_inode = nsfs_init_inode,
220 .put_data = nsfs_put_data,
221 };
222
nsfs_init_fs_context(struct fs_context * fc)223 static int nsfs_init_fs_context(struct fs_context *fc)
224 {
225 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC);
226 if (!ctx)
227 return -ENOMEM;
228 ctx->ops = &nsfs_ops;
229 ctx->dops = &ns_dentry_operations;
230 fc->s_fs_info = (void *)&nsfs_stashed_ops;
231 return 0;
232 }
233
234 static struct file_system_type nsfs = {
235 .name = "nsfs",
236 .init_fs_context = nsfs_init_fs_context,
237 .kill_sb = kill_anon_super,
238 };
239
nsfs_init(void)240 void __init nsfs_init(void)
241 {
242 nsfs_mnt = kern_mount(&nsfs);
243 if (IS_ERR(nsfs_mnt))
244 panic("can't set nsfs up\n");
245 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER;
246 }
247