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 __poll_t 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         __poll_t res = EPOLLIN | EPOLLRDNORM;
  27         int event;
  28
  29         poll_wait(file, &p->ns->poll, wait);
  30
  31         event = READ_ONCE(ns->event);
  32         if (m->poll_event != event) {
  33                 m->poll_event = event;
  34                 res |= EPOLLERR | EPOLLPRI;
  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                 { SB_SYNCHRONOUS, ",sync" },
  49                 { SB_DIRSYNC, ",dirsync" },
  50                 { SB_MANDLOCK, ",mand" },
  51                 { SB_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) {
  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_options)
 125                 err = sb->s_op->show_options(m, mnt_path.dentry);
 126         seq_puts(m, " 0 0\n");
 127 out:
 128         return err;
 129 }
 130
 131 static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
 132 {
 133         struct proc_mounts *p = m->private;
 134         struct mount *r = real_mount(mnt);
 135         struct super_block *sb = mnt->mnt_sb;
 136         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 137         int err;
 138
 139         seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
 140                    MAJOR(sb->s_dev), MINOR(sb->s_dev));
 141         if (sb->s_op->show_path) {
 142                 err = sb->s_op->show_path(m, mnt->mnt_root);
 143                 if (err)
 144                         goto out;
 145         } else {
 146                 seq_dentry(m, mnt->mnt_root, " \t\n\\");
 147         }
 148         seq_putc(m, ' ');
 149
 150         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 151         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 152         if (err)
 153                 goto out;
 154
 155         seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
 156         show_mnt_opts(m, mnt);
 157
 158         /* Tagged fields ("foo:X" or "bar") */
 159         if (IS_MNT_SHARED(r))
 160                 seq_printf(m, " shared:%i", r->mnt_group_id);
 161         if (IS_MNT_SLAVE(r)) {
 162                 int master = r->mnt_master->mnt_group_id;
 163                 int dom = get_dominating_id(r, &p->root);
 164                 seq_printf(m, " master:%i", master);
 165                 if (dom && dom != master)
 166                         seq_printf(m, " propagate_from:%i", dom);
 167         }
 168         if (IS_MNT_UNBINDABLE(r))
 169                 seq_puts(m, " unbindable");
 170
 171         /* Filesystem specific data */
 172         seq_puts(m, " - ");
 173         show_type(m, sb);
 174         seq_putc(m, ' ');
 175         if (sb->s_op->show_devname) {
 176                 err = sb->s_op->show_devname(m, mnt->mnt_root);
 177                 if (err)
 178                         goto out;
 179         } else {
 180                 mangle(m, r->mnt_devname ? r->mnt_devname : "none");
 181         }
 182         seq_puts(m, sb_rdonly(sb) ? " ro" : " rw");
 183         err = show_sb_opts(m, sb);
 184         if (err)
 185                 goto out;
 186         if (sb->s_op->show_options)
 187                 err = sb->s_op->show_options(m, mnt->mnt_root);
 188         seq_putc(m, '\n');
 189 out:
 190         return err;
 191 }
 192
 193 static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
 194 {
 195         struct proc_mounts *p = m->private;
 196         struct mount *r = real_mount(mnt);
 197         struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
 198         struct super_block *sb = mnt_path.dentry->d_sb;
 199         int err;
 200
 201         /* device */
 202         if (sb->s_op->show_devname) {
 203                 seq_puts(m, "device ");
 204                 err = sb->s_op->show_devname(m, mnt_path.dentry);
 205                 if (err)
 206                         goto out;
 207         } else {
 208                 if (r->mnt_devname) {
 209                         seq_puts(m, "device ");
 210                         mangle(m, r->mnt_devname);
 211                 } else
 212                         seq_puts(m, "no device");
 213         }
 214
 215         /* mount point */
 216         seq_puts(m, " mounted on ");
 217         /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
 218         err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
 219         if (err)
 220                 goto out;
 221         seq_putc(m, ' ');
 222
 223         /* file system type */
 224         seq_puts(m, "with fstype ");
 225         show_type(m, sb);
 226
 227         /* optional statistics */
 228         if (sb->s_op->show_stats) {
 229                 seq_putc(m, ' ');
 230                 err = sb->s_op->show_stats(m, mnt_path.dentry);
 231         }
 232
 233         seq_putc(m, '\n');
 234 out:
 235         return err;
 236 }
 237
 238 static int mounts_open_common(struct inode *inode, struct file *file,
 239                               int (*show)(struct seq_file *, struct vfsmount *))
 240 {
 241         struct task_struct *task = get_proc_task(inode);
 242         struct nsproxy *nsp;
 243         struct mnt_namespace *ns = NULL;
 244         struct path root;
 245         struct proc_mounts *p;
 246         struct seq_file *m;
 247         int ret = -EINVAL;
 248
 249         if (!task)
 250                 goto err;
 251
 252         task_lock(task);
 253         nsp = task->nsproxy;
 254         if (!nsp || !nsp->mnt_ns) {
 255                 task_unlock(task);
 256                 put_task_struct(task);
 257                 goto err;
 258         }
 259         ns = nsp->mnt_ns;
 260         get_mnt_ns(ns);
 261         if (!task->fs) {
 262                 task_unlock(task);
 263                 put_task_struct(task);
 264                 ret = -ENOENT;
 265                 goto err_put_ns;
 266         }
 267         get_fs_root(task->fs, &root);
 268         task_unlock(task);
 269         put_task_struct(task);
 270
 271         ret = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
 272         if (ret)
 273                 goto err_put_path;
 274
 275         m = file->private_data;
 276         m->poll_event = ns->event;
 277
 278         p = m->private;
 279         p->ns = ns;
 280         p->root = root;
 281         p->show = show;
 282         p->cached_event = ~0ULL;
 283
 284         return 0;
 285
 286  err_put_path:
 287         path_put(&root);
 288  err_put_ns:
 289         put_mnt_ns(ns);
 290  err:
 291         return ret;
 292 }
 293
 294 static int mounts_release(struct inode *inode, struct file *file)
 295 {
 296         struct seq_file *m = file->private_data;
 297         struct proc_mounts *p = m->private;
 298         path_put(&p->root);
 299         put_mnt_ns(p->ns);
 300         return seq_release_private(inode, file);
 301 }
 302
 303 static int mounts_open(struct inode *inode, struct file *file)
 304 {
 305         return mounts_open_common(inode, file, show_vfsmnt);
 306 }
 307
 308 static int mountinfo_open(struct inode *inode, struct file *file)
 309 {
 310         return mounts_open_common(inode, file, show_mountinfo);
 311 }
 312
 313 static int mountstats_open(struct inode *inode, struct file *file)
 314 {
 315         return mounts_open_common(inode, file, show_vfsstat);
 316 }
 317
 318 const struct file_operations proc_mounts_operations = {
 319         .open           = mounts_open,
 320         .read           = seq_read,
 321         .llseek         = seq_lseek,
 322         .release        = mounts_release,
 323         .poll           = mounts_poll,
 324 };
 325
 326 const struct file_operations proc_mountinfo_operations = {
 327         .open           = mountinfo_open,
 328         .read           = seq_read,
 329         .llseek         = seq_lseek,
 330         .release        = mounts_release,
 331         .poll           = mounts_poll,
 332 };
 333
 334 const struct file_operations proc_mountstats_operations = {
 335         .open           = mountstats_open,
 336         .read           = seq_read,
 337         .llseek         = seq_lseek,
 338         .release        = mounts_release,
 339 };