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 <linux/sched/task.h>
  14
  15 #include "proc/internal.h" /* only for get_proc_task() in ->open() */
  16
  17 #include "pnode.h"
  18 #include "internal.h"
  19
  20 static unsigned mounts_poll(struct file *file, poll_table *wait)
  21 {
  22         struct seq_file *m = file->private_data;
  23         struct proc_mounts *p = m->private;
  24         struct mnt_namespace *ns = p->ns;
  25         unsigned res = POLLIN | POLLRDNORM;
  26         int event;
  27
  28         poll_wait(file, &p->ns->poll, wait);
  29
  30         event = ACCESS_ONCE(ns->event);
  31         if (m->poll_event != event) {
  32                 m->poll_event = event;
  33                 res |= POLLERR | POLLPRI;
  34         }
  35
  36         return res;
  37 }
  38
  39 struct proc_fs_info {
  40         int flag;
  41         const char *str;
  42 };
  43
  44 static int show_sb_opts(struct seq_file *m, struct super_block *sb)
  45 {
  46         static const struct proc_fs_info fs_info[] = {
  47                 { MS_SYNCHRONOUS, ",sync" },
  48                 { MS_DIRSYNC, ",dirsync" },
  49                 { MS_MANDLOCK, ",mand" },
  50                 { MS_LAZYTIME, ",lazytime" },
  51                 { 0, NULL }
  52         };
  53         const struct proc_fs_info *fs_infop;
  54
  55         for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
  56                 if (sb->s_flags & fs_infop->flag)
  57                         seq_puts(m, fs_infop->str);
  58         }
  59
  60         return security_sb_show_options(m, sb);
  61 }
  62
  63 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
  64 {
  65         static const struct proc_fs_info mnt_info[] = {
  66                 { MNT_NOSUID, ",nosuid" },
  67                 { MNT_NODEV, ",nodev" },
  68                 { MNT_NOEXEC, ",noexec" },
  69                 { MNT_NOATIME, ",noatime" },
  70                 { MNT_NODIRATIME, ",nodiratime" },
  71                 { MNT_RELATIME, ",relatime" },
  72                 { 0, NULL }
  73         };
  74         const struct proc_fs_info *fs_infop;
  75
  76         for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
  77                 if (mnt->mnt_flags & fs_infop->flag)
  78                         seq_puts(m, fs_infop->str);
  79         }
  80 }
  81
  82 static inline void mangle(struct seq_file *m, const char *s)
  83 {
  84         seq_escape(m, s, " \t\n\\");
  85 }
  86
  87 static void show_type(struct seq_file *m, struct super_block *sb)
  88 {
  89         mangle(m, sb->s_type->name);
  90         if (sb->s_subtype && sb->s_subtype[0]) {
  91                 seq_putc(m, '.');
  92                 mangle(m, sb->s_subtype);
  93         }
  94 }
  95
  96 static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
  97 {
  98         struct proc_mounts *p = m->private;
  99         struct mount *r = real_mount(mnt);
 100         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 101         struct super_block *sb = mnt_path.dentry->d_sb;
 102         int err;
 103
 104         if (sb->s_op->show_devname) {
 105                 err = sb->s_op->show_devname(m, mnt_path.dentry);
 106                 if (err)
 107                         goto out;
 108         } else {
 109                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
 110         }
 111         seq_putc(m, ' ');
 112         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 113         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 114         if (err)
 115                 goto out;
 116         seq_putc(m, ' ');
 117         show_type(m, sb);
 118         seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
 119         err = show_sb_opts(m, sb);
 120         if (err)
 121                 goto out;
 122         show_mnt_opts(m, mnt);
 123         if (sb->s_op->show_options)
 124                 err = sb->s_op->show_options(m, mnt_path.dentry);
 125         seq_puts(m, " 0 0\n");
 126 out:
 127         return err;
 128 }
 129
 130 static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
 131 {
 132         struct proc_mounts *p = m->private;
 133         struct mount *r = real_mount(mnt);
 134         struct super_block *sb = mnt->mnt_sb;
 135         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 136         int err;
 137
 138         seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
 139                    MAJOR(sb->s_dev), MINOR(sb->s_dev));
 140         if (sb->s_op->show_path) {
 141                 err = sb->s_op->show_path(m, mnt->mnt_root);
 142                 if (err)
 143                         goto out;
 144         } else {
 145                 seq_dentry(m, mnt->mnt_root, " \t\n\\");
 146         }
 147         seq_putc(m, ' ');
 148
 149         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 150         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 151         if (err)
 152                 goto out;
 153
 154         seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
 155         show_mnt_opts(m, mnt);
 156
 157         /* Tagged fields ("foo:X" or "bar") */
 158         if (IS_MNT_SHARED(r))
 159                 seq_printf(m, " shared:%i", r->mnt_group_id);
 160         if (IS_MNT_SLAVE(r)) {
 161                 int master = r->mnt_master->mnt_group_id;
 162                 int dom = get_dominating_id(r, &p->root);
 163                 seq_printf(m, " master:%i", master);
 164                 if (dom && dom != master)
 165                         seq_printf(m, " propagate_from:%i", dom);
 166         }
 167         if (IS_MNT_UNBINDABLE(r))
 168                 seq_puts(m, " unbindable");
 169
 170         /* Filesystem specific data */
 171         seq_puts(m, " - ");
 172         show_type(m, sb);
 173         seq_putc(m, ' ');
 174         if (sb->s_op->show_devname) {
 175                 err = sb->s_op->show_devname(m, mnt->mnt_root);
 176                 if (err)
 177                         goto out;
 178         } else {
 179                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
 180         }
 181         seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
 182         err = show_sb_opts(m, sb);
 183         if (err)
 184                 goto out;
 185         if (sb->s_op->show_options)
 186                 err = sb->s_op->show_options(m, mnt->mnt_root);
 187         seq_putc(m, '\n');
 188 out:
 189         return err;
 190 }
 191
 192 static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
 193 {
 194         struct proc_mounts *p = m->private;
 195         struct mount *r = real_mount(mnt);
 196         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 197         struct super_block *sb = mnt_path.dentry->d_sb;
 198         int err;
 199
 200         /* device */
 201         if (sb->s_op->show_devname) {
 202                 seq_puts(m, "device ");
 203                 err = sb->s_op->show_devname(m, mnt_path.dentry);
 204                 if (err)
 205                         goto out;
 206         } else {
 207                 if (r->mnt_devname) {
 208                         seq_puts(m, "device ");
 209                         mangle(m, r->mnt_devname);
 210                 } else
 211                         seq_puts(m, "no device");
 212         }
 213
 214         /* mount point */
 215         seq_puts(m, " mounted on ");
 216         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 217         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 218         if (err)
 219                 goto out;
 220         seq_putc(m, ' ');
 221
 222         /* file system type */
 223         seq_puts(m, "with fstype ");
 224         show_type(m, sb);
 225
 226         /* optional statistics */
 227         if (sb->s_op->show_stats) {
 228                 seq_putc(m, ' ');
 229                 err = sb->s_op->show_stats(m, mnt_path.dentry);
 230         }
 231
 232         seq_putc(m, '\n');
 233 out:
 234         return err;
 235 }
 236
 237 static int mounts_open_common(struct inode *inode, struct file *file,
 238                               int (*show)(struct seq_file *, struct vfsmount *))
 239 {
 240         struct task_struct *task = get_proc_task(inode);
 241         struct nsproxy *nsp;
 242         struct mnt_namespace *ns = NULL;
 243         struct path root;
 244         struct proc_mounts *p;
 245         struct seq_file *m;
 246         int ret = -EINVAL;
 247
 248         if (!task)
 249                 goto err;
 250
 251         task_lock(task);
 252         nsp = task->nsproxy;
 253         if (!nsp || !nsp->mnt_ns) {
 254                 task_unlock(task);
 255                 put_task_struct(task);
 256                 goto err;
 257         }
 258         ns = nsp->mnt_ns;
 259         get_mnt_ns(ns);
 260         if (!task->fs) {
 261                 task_unlock(task);
 262                 put_task_struct(task);
 263                 ret = -ENOENT;
 264                 goto err_put_ns;
 265         }
 266         get_fs_root(task->fs, &root);
 267         task_unlock(task);
 268         put_task_struct(task);
 269
 270         ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
 271         if (ret)
 272                 goto err_put_path;
 273
 274         m = file->private_data;
 275         m->poll_event = ns->event;
 276
 277         p = m->private;
 278         p->ns = ns;
 279         p->root = root;
 280         p->show = show;
 281         p->cached_event = ~0ULL;
 282
 283         return 0;
 284
 285  err_put_path:
 286         path_put(&root);
 287  err_put_ns:
 288         put_mnt_ns(ns);
 289  err:
 290         return ret;
 291 }
 292
 293 static int mounts_release(struct inode *inode, struct file *file)
 294 {
 295         struct seq_file *m = file->private_data;
 296         struct proc_mounts *p = m->private;
 297         path_put(&p->root);
 298         put_mnt_ns(p->ns);
 299         return seq_release_private(inode, file);
 300 }
 301
 302 static int mounts_open(struct inode *inode, struct file *file)
 303 {
 304         return mounts_open_common(inode, file, show_vfsmnt);
 305 }
 306
 307 static int mountinfo_open(struct inode *inode, struct file *file)
 308 {
 309         return mounts_open_common(inode, file, show_mountinfo);
 310 }
 311
 312 static int mountstats_open(struct inode *inode, struct file *file)
 313 {
 314         return mounts_open_common(inode, file, show_vfsstat);
 315 }
 316
 317 const struct file_operations proc_mounts_operations = {
 318         .open           = mounts_open,
 319         .read           = seq_read,
 320         .llseek         = seq_lseek,
 321         .release        = mounts_release,
 322         .poll           = mounts_poll,
 323 };
 324
 325 const struct file_operations proc_mountinfo_operations = {
 326         .open           = mountinfo_open,
 327         .read           = seq_read,
 328         .llseek         = seq_lseek,
 329         .release        = mounts_release,
 330         .poll           = mounts_poll,
 331 };
 332
 333 const struct file_operations proc_mountstats_operations = {
 334         .open           = mountstats_open,
 335         .read           = seq_read,
 336         .llseek         = seq_lseek,
 337         .release        = mounts_release,
 338 };