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Linux/fs/proc_namespace.c

  1 /*
  2  * fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
  3  *
  4  * In fact, that's a piece of procfs; it's *almost* isolated from
  5  * the rest of fs/proc, but has rather close relationships with
  6  * fs/namespace.c, thus here instead of fs/proc
  7  *
  8  */
  9 #include <linux/mnt_namespace.h>
 10 #include <linux/nsproxy.h>
 11 #include <linux/security.h>
 12 #include <linux/fs_struct.h>
 13 #include "proc/internal.h" /* only for get_proc_task() in ->open() */
 14 
 15 #include "pnode.h"
 16 #include "internal.h"
 17 
 18 static unsigned mounts_poll(struct file *file, poll_table *wait)
 19 {
 20         struct seq_file *m = file->private_data;
 21         struct proc_mounts *p = m->private;
 22         struct mnt_namespace *ns = p->ns;
 23         unsigned res = POLLIN | POLLRDNORM;
 24         int event;
 25 
 26         poll_wait(file, &p->ns->poll, wait);
 27 
 28         event = ACCESS_ONCE(ns->event);
 29         if (m->poll_event != event) {
 30                 m->poll_event = event;
 31                 res |= POLLERR | POLLPRI;
 32         }
 33 
 34         return res;
 35 }
 36 
 37 struct proc_fs_info {
 38         int flag;
 39         const char *str;
 40 };
 41 
 42 static int show_sb_opts(struct seq_file *m, struct super_block *sb)
 43 {
 44         static const struct proc_fs_info fs_info[] = {
 45                 { MS_SYNCHRONOUS, ",sync" },
 46                 { MS_DIRSYNC, ",dirsync" },
 47                 { MS_MANDLOCK, ",mand" },
 48                 { MS_LAZYTIME, ",lazytime" },
 49                 { 0, NULL }
 50         };
 51         const struct proc_fs_info *fs_infop;
 52 
 53         for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
 54                 if (sb->s_flags & fs_infop->flag)
 55                         seq_puts(m, fs_infop->str);
 56         }
 57 
 58         return security_sb_show_options(m, sb);
 59 }
 60 
 61 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
 62 {
 63         static const struct proc_fs_info mnt_info[] = {
 64                 { MNT_NOSUID, ",nosuid" },
 65                 { MNT_NODEV, ",nodev" },
 66                 { MNT_NOEXEC, ",noexec" },
 67                 { MNT_NOATIME, ",noatime" },
 68                 { MNT_NODIRATIME, ",nodiratime" },
 69                 { MNT_RELATIME, ",relatime" },
 70                 { 0, NULL }
 71         };
 72         const struct proc_fs_info *fs_infop;
 73 
 74         for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
 75                 if (mnt->mnt_flags & fs_infop->flag)
 76                         seq_puts(m, fs_infop->str);
 77         }
 78 }
 79 
 80 static inline void mangle(struct seq_file *m, const char *s)
 81 {
 82         seq_escape(m, s, " \t\n\\");
 83 }
 84 
 85 static void show_type(struct seq_file *m, struct super_block *sb)
 86 {
 87         mangle(m, sb->s_type->name);
 88         if (sb->s_subtype && sb->s_subtype[0]) {
 89                 seq_putc(m, '.');
 90                 mangle(m, sb->s_subtype);
 91         }
 92 }
 93 
 94 static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
 95 {
 96         struct proc_mounts *p = m->private;
 97         struct mount *r = real_mount(mnt);
 98         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 99         struct super_block *sb = mnt_path.dentry->d_sb;
100         int err;
101 
102         if (sb->s_op->show_devname) {
103                 err = sb->s_op->show_devname(m, mnt_path.dentry);
104                 if (err)
105                         goto out;
106         } else {
107                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
108         }
109         seq_putc(m, ' ');
110         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
111         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
112         if (err)
113                 goto out;
114         seq_putc(m, ' ');
115         show_type(m, sb);
116         seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
117         err = show_sb_opts(m, sb);
118         if (err)
119                 goto out;
120         show_mnt_opts(m, mnt);
121         if (sb->s_op->show_options)
122                 err = sb->s_op->show_options(m, mnt_path.dentry);
123         seq_puts(m, " 0 0\n");
124 out:
125         return err;
126 }
127 
128 static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
129 {
130         struct proc_mounts *p = m->private;
131         struct mount *r = real_mount(mnt);
132         struct super_block *sb = mnt->mnt_sb;
133         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
134         int err;
135 
136         seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
137                    MAJOR(sb->s_dev), MINOR(sb->s_dev));
138         if (sb->s_op->show_path) {
139                 err = sb->s_op->show_path(m, mnt->mnt_root);
140                 if (err)
141                         goto out;
142         } else {
143                 seq_dentry(m, mnt->mnt_root, " \t\n\\");
144         }
145         seq_putc(m, ' ');
146 
147         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
148         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
149         if (err)
150                 goto out;
151 
152         seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
153         show_mnt_opts(m, mnt);
154 
155         /* Tagged fields ("foo:X" or "bar") */
156         if (IS_MNT_SHARED(r))
157                 seq_printf(m, " shared:%i", r->mnt_group_id);
158         if (IS_MNT_SLAVE(r)) {
159                 int master = r->mnt_master->mnt_group_id;
160                 int dom = get_dominating_id(r, &p->root);
161                 seq_printf(m, " master:%i", master);
162                 if (dom && dom != master)
163                         seq_printf(m, " propagate_from:%i", dom);
164         }
165         if (IS_MNT_UNBINDABLE(r))
166                 seq_puts(m, " unbindable");
167 
168         /* Filesystem specific data */
169         seq_puts(m, " - ");
170         show_type(m, sb);
171         seq_putc(m, ' ');
172         if (sb->s_op->show_devname) {
173                 err = sb->s_op->show_devname(m, mnt->mnt_root);
174                 if (err)
175                         goto out;
176         } else {
177                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
178         }
179         seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
180         err = show_sb_opts(m, sb);
181         if (err)
182                 goto out;
183         if (sb->s_op->show_options)
184                 err = sb->s_op->show_options(m, mnt->mnt_root);
185         seq_putc(m, '\n');
186 out:
187         return err;
188 }
189 
190 static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
191 {
192         struct proc_mounts *p = m->private;
193         struct mount *r = real_mount(mnt);
194         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
195         struct super_block *sb = mnt_path.dentry->d_sb;
196         int err;
197 
198         /* device */
199         if (sb->s_op->show_devname) {
200                 seq_puts(m, "device ");
201                 err = sb->s_op->show_devname(m, mnt_path.dentry);
202                 if (err)
203                         goto out;
204         } else {
205                 if (r->mnt_devname) {
206                         seq_puts(m, "device ");
207                         mangle(m, r->mnt_devname);
208                 } else
209                         seq_puts(m, "no device");
210         }
211 
212         /* mount point */
213         seq_puts(m, " mounted on ");
214         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
215         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
216         if (err)
217                 goto out;
218         seq_putc(m, ' ');
219 
220         /* file system type */
221         seq_puts(m, "with fstype ");
222         show_type(m, sb);
223 
224         /* optional statistics */
225         if (sb->s_op->show_stats) {
226                 seq_putc(m, ' ');
227                 err = sb->s_op->show_stats(m, mnt_path.dentry);
228         }
229 
230         seq_putc(m, '\n');
231 out:
232         return err;
233 }
234 
235 static int mounts_open_common(struct inode *inode, struct file *file,
236                               int (*show)(struct seq_file *, struct vfsmount *))
237 {
238         struct task_struct *task = get_proc_task(inode);
239         struct nsproxy *nsp;
240         struct mnt_namespace *ns = NULL;
241         struct path root;
242         struct proc_mounts *p;
243         struct seq_file *m;
244         int ret = -EINVAL;
245 
246         if (!task)
247                 goto err;
248 
249         task_lock(task);
250         nsp = task->nsproxy;
251         if (!nsp || !nsp->mnt_ns) {
252                 task_unlock(task);
253                 put_task_struct(task);
254                 goto err;
255         }
256         ns = nsp->mnt_ns;
257         get_mnt_ns(ns);
258         if (!task->fs) {
259                 task_unlock(task);
260                 put_task_struct(task);
261                 ret = -ENOENT;
262                 goto err_put_ns;
263         }
264         get_fs_root(task->fs, &root);
265         task_unlock(task);
266         put_task_struct(task);
267 
268         ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
269         if (ret)
270                 goto err_put_path;
271 
272         m = file->private_data;
273         m->poll_event = ns->event;
274 
275         p = m->private;
276         p->ns = ns;
277         p->root = root;
278         p->show = show;
279         p->cached_event = ~0ULL;
280 
281         return 0;
282 
283  err_put_path:
284         path_put(&root);
285  err_put_ns:
286         put_mnt_ns(ns);
287  err:
288         return ret;
289 }
290 
291 static int mounts_release(struct inode *inode, struct file *file)
292 {
293         struct seq_file *m = file->private_data;
294         struct proc_mounts *p = m->private;
295         path_put(&p->root);
296         put_mnt_ns(p->ns);
297         return seq_release_private(inode, file);
298 }
299 
300 static int mounts_open(struct inode *inode, struct file *file)
301 {
302         return mounts_open_common(inode, file, show_vfsmnt);
303 }
304 
305 static int mountinfo_open(struct inode *inode, struct file *file)
306 {
307         return mounts_open_common(inode, file, show_mountinfo);
308 }
309 
310 static int mountstats_open(struct inode *inode, struct file *file)
311 {
312         return mounts_open_common(inode, file, show_vfsstat);
313 }
314 
315 const struct file_operations proc_mounts_operations = {
316         .open           = mounts_open,
317         .read           = seq_read,
318         .llseek         = seq_lseek,
319         .release        = mounts_release,
320         .poll           = mounts_poll,
321 };
322 
323 const struct file_operations proc_mountinfo_operations = {
324         .open           = mountinfo_open,
325         .read           = seq_read,
326         .llseek         = seq_lseek,
327         .release        = mounts_release,
328         .poll           = mounts_poll,
329 };
330 
331 const struct file_operations proc_mountstats_operations = {
332         .open           = mountstats_open,
333         .read           = seq_read,
334         .llseek         = seq_lseek,
335         .release        = mounts_release,
336 };
337 

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