fs/proc_namespace.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
   4  *
   5  * In fact, that's a piece of procfs; it's *almost* isolated from
   6  * the rest of fs/proc, but has rather close relationships with
   7  * fs/namespace.c, thus here instead of fs/proc
   8  *
   9  */
  10 #include <linux/mnt_namespace.h>
  11 #include <linux/nsproxy.h>
  12 #include <linux/security.h>
  13 #include <linux/fs_struct.h>
  14 #include <linux/sched/task.h>
  15
  16 #include "proc/internal.h" /* only for get_proc_task() in ->open() */
  17
  18 #include "pnode.h"
  19 #include "internal.h"
  20
  21 static unsigned mounts_poll(struct file *file, poll_table *wait)
  22 {
  23         struct seq_file *m = file->private_data;
  24         struct proc_mounts *p = m->private;
  25         struct mnt_namespace *ns = p->ns;
  26         unsigned res = POLLIN | POLLRDNORM;
  27         int event;
  28
  29         poll_wait(file, &p->ns->poll, wait);
  30
  31         event = ACCESS_ONCE(ns->event);
  32         if (m->poll_event != event) {
  33                 m->poll_event = event;
  34                 res |= POLLERR | POLLPRI;
  35         }
  36
  37         return res;
  38 }
  39
  40 struct proc_fs_info {
  41         int flag;
  42         const char *str;
  43 };
  44
  45 static int show_sb_opts(struct seq_file *m, struct super_block *sb)
  46 {
  47         static const struct proc_fs_info fs_info[] = {
  48                 { MS_SYNCHRONOUS, ",sync" },
  49                 { MS_DIRSYNC, ",dirsync" },
  50                 { MS_MANDLOCK, ",mand" },
  51                 { MS_LAZYTIME, ",lazytime" },
  52                 { 0, NULL }
  53         };
  54         const struct proc_fs_info *fs_infop;
  55
  56         for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
  57                 if (sb->s_flags & fs_infop->flag)
  58                         seq_puts(m, fs_infop->str);
  59         }
  60
  61         return security_sb_show_options(m, sb);
  62 }
  63
  64 static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
  65 {
  66         static const struct proc_fs_info mnt_info[] = {
  67                 { MNT_NOSUID, ",nosuid" },
  68                 { MNT_NODEV, ",nodev" },
  69                 { MNT_NOEXEC, ",noexec" },
  70                 { MNT_NOATIME, ",noatime" },
  71                 { MNT_NODIRATIME, ",nodiratime" },
  72                 { MNT_RELATIME, ",relatime" },
  73                 { 0, NULL }
  74         };
  75         const struct proc_fs_info *fs_infop;
  76
  77         for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
  78                 if (mnt->mnt_flags & fs_infop->flag)
  79                         seq_puts(m, fs_infop->str);
  80         }
  81 }
  82
  83 static inline void mangle(struct seq_file *m, const char *s)
  84 {
  85         seq_escape(m, s, " \t\n\\");
  86 }
  87
  88 static void show_type(struct seq_file *m, struct super_block *sb)
  89 {
  90         mangle(m, sb->s_type->name);
  91         if (sb->s_subtype && sb->s_subtype[0]) {
  92                 seq_putc(m, '.');
  93                 mangle(m, sb->s_subtype);
  94         }
  95 }
  96
  97 static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
  98 {
  99         struct proc_mounts *p = m->private;
 100         struct mount *r = real_mount(mnt);
 101         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 102         struct super_block *sb = mnt_path.dentry->d_sb;
 103         int err;
 104
 105         if (sb->s_op->show_devname) {
 106                 err = sb->s_op->show_devname(m, mnt_path.dentry);
 107                 if (err)
 108                         goto out;
 109         } else {
 110                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
 111         }
 112         seq_putc(m, ' ');
 113         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 114         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 115         if (err)
 116                 goto out;
 117         seq_putc(m, ' ');
 118         show_type(m, sb);
 119         seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
 120         err = show_sb_opts(m, sb);
 121         if (err)
 122                 goto out;
 123         show_mnt_opts(m, mnt);
 124         if (sb->s_op->show_options2)
 125                         err = sb->s_op->show_options2(mnt, m, mnt_path.dentry);
 126         else if (sb->s_op->show_options)
 127                 err = sb->s_op->show_options(m, mnt_path.dentry);
 128         seq_puts(m, " 0 0\n");
 129 out:
 130         return err;
 131 }
 132
 133 static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
 134 {
 135         struct proc_mounts *p = m->private;
 136         struct mount *r = real_mount(mnt);
 137         struct super_block *sb = mnt->mnt_sb;
 138         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 139         int err;
 140
 141         seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
 142                    MAJOR(sb->s_dev), MINOR(sb->s_dev));
 143         if (sb->s_op->show_path) {
 144                 err = sb->s_op->show_path(m, mnt->mnt_root);
 145                 if (err)
 146                         goto out;
 147         } else {
 148                 seq_dentry(m, mnt->mnt_root, " \t\n\\");
 149         }
 150         seq_putc(m, ' ');
 151
 152         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 153         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 154         if (err)
 155                 goto out;
 156
 157         seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
 158         show_mnt_opts(m, mnt);
 159
 160         /* Tagged fields ("foo:X" or "bar") */
 161         if (IS_MNT_SHARED(r))
 162                 seq_printf(m, " shared:%i", r->mnt_group_id);
 163         if (IS_MNT_SLAVE(r)) {
 164                 int master = r->mnt_master->mnt_group_id;
 165                 int dom = get_dominating_id(r, &p->root);
 166                 seq_printf(m, " master:%i", master);
 167                 if (dom && dom != master)
 168                         seq_printf(m, " propagate_from:%i", dom);
 169         }
 170         if (IS_MNT_UNBINDABLE(r))
 171                 seq_puts(m, " unbindable");
 172
 173         /* Filesystem specific data */
 174         seq_puts(m, " - ");
 175         show_type(m, sb);
 176         seq_putc(m, ' ');
 177         if (sb->s_op->show_devname) {
 178                 err = sb->s_op->show_devname(m, mnt->mnt_root);
 179                 if (err)
 180                         goto out;
 181         } else {
 182                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
 183         }
 184         seq_puts(m, sb_rdonly(sb) ? " ro" : " rw");
 185         err = show_sb_opts(m, sb);
 186         if (err)
 187                 goto out;
 188         if (sb->s_op->show_options2) {
 189                 err = sb->s_op->show_options2(mnt, m, mnt->mnt_root);
 190         } else if (sb->s_op->show_options)
 191                 err = sb->s_op->show_options(m, mnt->mnt_root);
 192         seq_putc(m, '\n');
 193 out:
 194         return err;
 195 }
 196
 197 static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
 198 {
 199         struct proc_mounts *p = m->private;
 200         struct mount *r = real_mount(mnt);
 201         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 202         struct super_block *sb = mnt_path.dentry->d_sb;
 203         int err;
 204
 205         /* device */
 206         if (sb->s_op->show_devname) {
 207                 seq_puts(m, "device ");
 208                 err = sb->s_op->show_devname(m, mnt_path.dentry);
 209                 if (err)
 210                         goto out;
 211         } else {
 212                 if (r->mnt_devname) {
 213                         seq_puts(m, "device ");
 214                         mangle(m, r->mnt_devname);
 215                 } else
 216                         seq_puts(m, "no device");
 217         }
 218
 219         /* mount point */
 220         seq_puts(m, " mounted on ");
 221         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 222         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 223         if (err)
 224                 goto out;
 225         seq_putc(m, ' ');
 226
 227         /* file system type */
 228         seq_puts(m, "with fstype ");
 229         show_type(m, sb);
 230
 231         /* optional statistics */
 232         if (sb->s_op->show_stats) {
 233                 seq_putc(m, ' ');
 234                 err = sb->s_op->show_stats(m, mnt_path.dentry);
 235         }
 236
 237         seq_putc(m, '\n');
 238 out:
 239         return err;
 240 }
 241
 242 static int mounts_open_common(struct inode *inode, struct file *file,
 243                               int (*show)(struct seq_file *, struct vfsmount *))
 244 {
 245         struct task_struct *task = get_proc_task(inode);
 246         struct nsproxy *nsp;
 247         struct mnt_namespace *ns = NULL;
 248         struct path root;
 249         struct proc_mounts *p;
 250         struct seq_file *m;
 251         int ret = -EINVAL;
 252
 253         if (!task)
 254                 goto err;
 255
 256         task_lock(task);
 257         nsp = task->nsproxy;
 258         if (!nsp || !nsp->mnt_ns) {
 259                 task_unlock(task);
 260                 put_task_struct(task);
 261                 goto err;
 262         }
 263         ns = nsp->mnt_ns;
 264         get_mnt_ns(ns);
 265         if (!task->fs) {
 266                 task_unlock(task);
 267                 put_task_struct(task);
 268                 ret = -ENOENT;
 269                 goto err_put_ns;
 270         }
 271         get_fs_root(task->fs, &root);
 272         task_unlock(task);
 273         put_task_struct(task);
 274
 275         ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
 276         if (ret)
 277                 goto err_put_path;
 278
 279         m = file->private_data;
 280         m->poll_event = ns->event;
 281
 282         p = m->private;
 283         p->ns = ns;
 284         p->root = root;
 285         p->show = show;
 286         p->cached_event = ~0ULL;
 287
 288         return 0;
 289
 290  err_put_path:
 291         path_put(&root);
 292  err_put_ns:
 293         put_mnt_ns(ns);
 294  err:
 295         return ret;
 296 }
 297
 298 static int mounts_release(struct inode *inode, struct file *file)
 299 {
 300         struct seq_file *m = file->private_data;
 301         struct proc_mounts *p = m->private;
 302         path_put(&p->root);
 303         put_mnt_ns(p->ns);
 304         return seq_release_private(inode, file);
 305 }
 306
 307 static int mounts_open(struct inode *inode, struct file *file)
 308 {
 309         return mounts_open_common(inode, file, show_vfsmnt);
 310 }
 311
 312 static int mountinfo_open(struct inode *inode, struct file *file)
 313 {
 314         return mounts_open_common(inode, file, show_mountinfo);
 315 }
 316
 317 static int mountstats_open(struct inode *inode, struct file *file)
 318 {
 319         return mounts_open_common(inode, file, show_vfsstat);
 320 }
 321
 322 const struct file_operations proc_mounts_operations = {
 323         .open           = mounts_open,
 324         .read           = seq_read,
 325         .llseek         = seq_lseek,
 326         .release        = mounts_release,
 327         .poll           = mounts_poll,
 328 };
 329
 330 const struct file_operations proc_mountinfo_operations = {
 331         .open           = mountinfo_open,
 332         .read           = seq_read,
 333         .llseek         = seq_lseek,
 334         .release        = mounts_release,
 335         .poll           = mounts_poll,
 336 };
 337
 338 const struct file_operations proc_mountstats_operations = {
 339         .open           = mountstats_open,
 340         .read           = seq_read,
 341         .llseek         = seq_lseek,
 342         .release        = mounts_release,
 343 };