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