linux/fs/proc_namespace.c
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   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
  18static unsigned mounts_poll(struct file *file, poll_table *wait)
  19{
  20        struct proc_mounts *p = file->private_data;
  21        struct mnt_namespace *ns = p->ns;
  22        unsigned res = POLLIN | POLLRDNORM;
  23
  24        poll_wait(file, &p->ns->poll, wait);
  25
  26        br_read_lock(&vfsmount_lock);
  27        if (p->m.poll_event != ns->event) {
  28                p->m.poll_event = ns->event;
  29                res |= POLLERR | POLLPRI;
  30        }
  31        br_read_unlock(&vfsmount_lock);
  32
  33        return res;
  34}
  35
  36struct proc_fs_info {
  37        int flag;
  38        const char *str;
  39};
  40
  41static 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
  59static 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
  78static inline void mangle(struct seq_file *m, const char *s)
  79{
  80        seq_escape(m, s, " \t\n\\");
  81}
  82
  83static 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
  92static 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");
 118out:
 119        return err;
 120}
 121
 122static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
 123{
 124        struct proc_mounts *p = m->private;
 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');
 179out:
 180        return err;
 181}
 182
 183static 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
 222static 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->m.private = p;
 272        p->ns = ns;
 273        p->root = root;
 274        p->m.poll_event = ns->event;
 275        p->show = show;
 276
 277        return 0;
 278
 279 err_free:
 280        kfree(p);
 281 err_put_path:
 282        path_put(&root);
 283 err_put_ns:
 284        put_mnt_ns(ns);
 285 err:
 286        return ret;
 287}
 288
 289static int mounts_release(struct inode *inode, struct file *file)
 290{
 291        struct proc_mounts *p = file->private_data;
 292        path_put(&p->root);
 293        put_mnt_ns(p->ns);
 294        return seq_release(inode, file);
 295}
 296
 297static int mounts_open(struct inode *inode, struct file *file)
 298{
 299        return mounts_open_common(inode, file, show_vfsmnt);
 300}
 301
 302static int mountinfo_open(struct inode *inode, struct file *file)
 303{
 304        return mounts_open_common(inode, file, show_mountinfo);
 305}
 306
 307static int mountstats_open(struct inode *inode, struct file *file)
 308{
 309        return mounts_open_common(inode, file, show_vfsstat);
 310}
 311
 312const struct file_operations proc_mounts_operations = {
 313        .open           = mounts_open,
 314        .read           = seq_read,
 315        .llseek         = seq_lseek,
 316        .release        = mounts_release,
 317        .poll           = mounts_poll,
 318};
 319
 320const struct file_operations proc_mountinfo_operations = {
 321        .open           = mountinfo_open,
 322        .read           = seq_read,
 323        .llseek         = seq_lseek,
 324        .release        = mounts_release,
 325        .poll           = mounts_poll,
 326};
 327
 328const struct file_operations proc_mountstats_operations = {
 329        .open           = mountstats_open,
 330        .read           = seq_read,
 331        .llseek         = seq_lseek,
 332        .release        = mounts_release,
 333};
 334
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