Version:  2.0.40 2.2.26 2.4.37 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10

Linux/fs/nsfs.c

  1 #include <linux/mount.h>
  2 #include <linux/file.h>
  3 #include <linux/fs.h>
  4 #include <linux/proc_ns.h>
  5 #include <linux/magic.h>
  6 #include <linux/ktime.h>
  7 #include <linux/seq_file.h>
  8 #include <linux/user_namespace.h>
  9 #include <linux/nsfs.h>
 10 
 11 static struct vfsmount *nsfs_mnt;
 12 
 13 static long ns_ioctl(struct file *filp, unsigned int ioctl,
 14                         unsigned long arg);
 15 static const struct file_operations ns_file_operations = {
 16         .llseek         = no_llseek,
 17         .unlocked_ioctl = ns_ioctl,
 18 };
 19 
 20 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen)
 21 {
 22         struct inode *inode = d_inode(dentry);
 23         const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
 24 
 25         return dynamic_dname(dentry, buffer, buflen, "%s:[%lu]",
 26                 ns_ops->name, inode->i_ino);
 27 }
 28 
 29 static void ns_prune_dentry(struct dentry *dentry)
 30 {
 31         struct inode *inode = d_inode(dentry);
 32         if (inode) {
 33                 struct ns_common *ns = inode->i_private;
 34                 atomic_long_set(&ns->stashed, 0);
 35         }
 36 }
 37 
 38 const struct dentry_operations ns_dentry_operations =
 39 {
 40         .d_prune        = ns_prune_dentry,
 41         .d_delete       = always_delete_dentry,
 42         .d_dname        = ns_dname,
 43 };
 44 
 45 static void nsfs_evict(struct inode *inode)
 46 {
 47         struct ns_common *ns = inode->i_private;
 48         clear_inode(inode);
 49         ns->ops->put(ns);
 50 }
 51 
 52 static void *__ns_get_path(struct path *path, struct ns_common *ns)
 53 {
 54         struct vfsmount *mnt = nsfs_mnt;
 55         struct qstr qname = { .name = "", };
 56         struct dentry *dentry;
 57         struct inode *inode;
 58         unsigned long d;
 59 
 60         rcu_read_lock();
 61         d = atomic_long_read(&ns->stashed);
 62         if (!d)
 63                 goto slow;
 64         dentry = (struct dentry *)d;
 65         if (!lockref_get_not_dead(&dentry->d_lockref))
 66                 goto slow;
 67         rcu_read_unlock();
 68         ns->ops->put(ns);
 69 got_it:
 70         path->mnt = mntget(mnt);
 71         path->dentry = dentry;
 72         return NULL;
 73 slow:
 74         rcu_read_unlock();
 75         inode = new_inode_pseudo(mnt->mnt_sb);
 76         if (!inode) {
 77                 ns->ops->put(ns);
 78                 return ERR_PTR(-ENOMEM);
 79         }
 80         inode->i_ino = ns->inum;
 81         inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
 82         inode->i_flags |= S_IMMUTABLE;
 83         inode->i_mode = S_IFREG | S_IRUGO;
 84         inode->i_fop = &ns_file_operations;
 85         inode->i_private = ns;
 86 
 87         dentry = d_alloc_pseudo(mnt->mnt_sb, &qname);
 88         if (!dentry) {
 89                 iput(inode);
 90                 return ERR_PTR(-ENOMEM);
 91         }
 92         d_instantiate(dentry, inode);
 93         dentry->d_fsdata = (void *)ns->ops;
 94         d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry);
 95         if (d) {
 96                 d_delete(dentry);       /* make sure ->d_prune() does nothing */
 97                 dput(dentry);
 98                 cpu_relax();
 99                 return ERR_PTR(-EAGAIN);
100         }
101         goto got_it;
102 }
103 
104 void *ns_get_path(struct path *path, struct task_struct *task,
105                         const struct proc_ns_operations *ns_ops)
106 {
107         struct ns_common *ns;
108         void *ret;
109 
110 again:
111         ns = ns_ops->get(task);
112         if (!ns)
113                 return ERR_PTR(-ENOENT);
114 
115         ret = __ns_get_path(path, ns);
116         if (IS_ERR(ret) && PTR_ERR(ret) == -EAGAIN)
117                 goto again;
118         return ret;
119 }
120 
121 int open_related_ns(struct ns_common *ns,
122                    struct ns_common *(*get_ns)(struct ns_common *ns))
123 {
124         struct path path = {};
125         struct file *f;
126         void *err;
127         int fd;
128 
129         fd = get_unused_fd_flags(O_CLOEXEC);
130         if (fd < 0)
131                 return fd;
132 
133         while (1) {
134                 struct ns_common *relative;
135 
136                 relative = get_ns(ns);
137                 if (IS_ERR(relative)) {
138                         put_unused_fd(fd);
139                         return PTR_ERR(relative);
140                 }
141 
142                 err = __ns_get_path(&path, relative);
143                 if (IS_ERR(err) && PTR_ERR(err) == -EAGAIN)
144                         continue;
145                 break;
146         }
147         if (IS_ERR(err)) {
148                 put_unused_fd(fd);
149                 return PTR_ERR(err);
150         }
151 
152         f = dentry_open(&path, O_RDONLY, current_cred());
153         path_put(&path);
154         if (IS_ERR(f)) {
155                 put_unused_fd(fd);
156                 fd = PTR_ERR(f);
157         } else
158                 fd_install(fd, f);
159 
160         return fd;
161 }
162 
163 static long ns_ioctl(struct file *filp, unsigned int ioctl,
164                         unsigned long arg)
165 {
166         struct ns_common *ns = get_proc_ns(file_inode(filp));
167 
168         switch (ioctl) {
169         case NS_GET_USERNS:
170                 return open_related_ns(ns, ns_get_owner);
171         case NS_GET_PARENT:
172                 if (!ns->ops->get_parent)
173                         return -EINVAL;
174                 return open_related_ns(ns, ns->ops->get_parent);
175         default:
176                 return -ENOTTY;
177         }
178 }
179 
180 int ns_get_name(char *buf, size_t size, struct task_struct *task,
181                         const struct proc_ns_operations *ns_ops)
182 {
183         struct ns_common *ns;
184         int res = -ENOENT;
185         ns = ns_ops->get(task);
186         if (ns) {
187                 res = snprintf(buf, size, "%s:[%u]", ns_ops->name, ns->inum);
188                 ns_ops->put(ns);
189         }
190         return res;
191 }
192 
193 struct file *proc_ns_fget(int fd)
194 {
195         struct file *file;
196 
197         file = fget(fd);
198         if (!file)
199                 return ERR_PTR(-EBADF);
200 
201         if (file->f_op != &ns_file_operations)
202                 goto out_invalid;
203 
204         return file;
205 
206 out_invalid:
207         fput(file);
208         return ERR_PTR(-EINVAL);
209 }
210 
211 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry)
212 {
213         struct inode *inode = d_inode(dentry);
214         const struct proc_ns_operations *ns_ops = dentry->d_fsdata;
215 
216         seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino);
217         return 0;
218 }
219 
220 static const struct super_operations nsfs_ops = {
221         .statfs = simple_statfs,
222         .evict_inode = nsfs_evict,
223         .show_path = nsfs_show_path,
224 };
225 static struct dentry *nsfs_mount(struct file_system_type *fs_type,
226                         int flags, const char *dev_name, void *data)
227 {
228         return mount_pseudo(fs_type, "nsfs:", &nsfs_ops,
229                         &ns_dentry_operations, NSFS_MAGIC);
230 }
231 static struct file_system_type nsfs = {
232         .name = "nsfs",
233         .mount = nsfs_mount,
234         .kill_sb = kill_anon_super,
235 };
236 
237 void __init nsfs_init(void)
238 {
239         nsfs_mnt = kern_mount(&nsfs);
240         if (IS_ERR(nsfs_mnt))
241                 panic("can't set nsfs up\n");
242         nsfs_mnt->mnt_sb->s_flags &= ~MS_NOUSER;
243 }
244 

This page was automatically generated by LXR 0.3.1 (source).  •  Linux is a registered trademark of Linus Torvalds  •  Contact us