proc_namespace.c

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/*
 * fs/proc_namespace.c - handling of /proc/<pid>/{mounts,mountinfo,mountstats}
 *
 * In fact, that's a piece of procfs; it's *almost* isolated from
 * the rest of fs/proc, but has rather close relationships with
 * fs/namespace.c, thus here instead of fs/proc
 *
 */
#include <linux/mnt_namespace.h>
#include <linux/nsproxy.h>
#include <linux/security.h>
#include <linux/fs_struct.h>
#include "proc/internal.h" /* only for get_proc_task() in ->open() */

#include "pnode.h"
#include "internal.h"

static unsigned mounts_poll(struct file *file, poll_table *wait)
{
    struct proc_mounts *p = proc_mounts(file->private_data);
    struct mnt_namespace *ns = p->ns;
    unsigned res = POLLIN | POLLRDNORM;

    poll_wait(file, &p->ns->poll, wait);

    br_read_lock(&vfsmount_lock);
    if (p->m.poll_event != ns->event) {
        p->m.poll_event = ns->event;
        res |= POLLERR | POLLPRI;
    }
    br_read_unlock(&vfsmount_lock);

    return res;
}

struct proc_fs_info {
    int flag;
    const char *str;
};

static int show_sb_opts(struct seq_file *m, struct super_block *sb)
{
    static const struct proc_fs_info fs_info[] = {
        { MS_SYNCHRONOUS, ",sync" },
        { MS_DIRSYNC, ",dirsync" },
        { MS_MANDLOCK, ",mand" },
        { 0, NULL }
    };
    const struct proc_fs_info *fs_infop;

    for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
        if (sb->s_flags & fs_infop->flag)
            seq_puts(m, fs_infop->str);
    }

    return security_sb_show_options(m, sb);
}

static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
{
    static const struct proc_fs_info mnt_info[] = {
        { MNT_NOSUID, ",nosuid" },
        { MNT_NODEV, ",nodev" },
        { MNT_NOEXEC, ",noexec" },
        { MNT_NOATIME, ",noatime" },
        { MNT_NODIRATIME, ",nodiratime" },
        { MNT_RELATIME, ",relatime" },
        { 0, NULL }
    };
    const struct proc_fs_info *fs_infop;

    for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
        if (mnt->mnt_flags & fs_infop->flag)
            seq_puts(m, fs_infop->str);
    }
}

static inline void mangle(struct seq_file *m, const char *s)
{
    seq_escape(m, s, " \t\n\\");
}

static void show_type(struct seq_file *m, struct super_block *sb)
{
    mangle(m, sb->s_type->name);
    if (sb->s_subtype && sb->s_subtype[0]) {
        seq_putc(m, '.');
        mangle(m, sb->s_subtype);
    }
}

static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
{
    struct mount *r = real_mount(mnt);
    int err = 0;
    struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
    struct super_block *sb = mnt_path.dentry->d_sb;

    if (sb->s_op->show_devname) {
        err = sb->s_op->show_devname(m, mnt_path.dentry);
        if (err)
            goto out;
    } else {
        mangle(m, r->mnt_devname ? r->mnt_devname : "none");
    }
    seq_putc(m, ' ');
    seq_path(m, &mnt_path, " \t\n\\");
    seq_putc(m, ' ');
    show_type(m, sb);
    seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
    err = show_sb_opts(m, sb);
    if (err)
        goto out;
    show_mnt_opts(m, mnt);
    if (sb->s_op->show_options)
        err = sb->s_op->show_options(m, mnt_path.dentry);
    seq_puts(m, " 0 0\n");
out:
    return err;
}

static int show_mountinfo(struct seq_file *m, struct vfsmount *mnt)
{
    struct proc_mounts *p = proc_mounts(m);
    struct mount *r = real_mount(mnt);
    struct super_block *sb = mnt->mnt_sb;
    struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
    struct path root = p->root;
    int err = 0;

    seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
           MAJOR(sb->s_dev), MINOR(sb->s_dev));
    if (sb->s_op->show_path)
        err = sb->s_op->show_path(m, mnt->mnt_root);
    else
        seq_dentry(m, mnt->mnt_root, " \t\n\\");
    if (err)
        goto out;
    seq_putc(m, ' ');

    /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
    err = seq_path_root(m, &mnt_path, &root, " \t\n\\");
    if (err)
        goto out;

    seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
    show_mnt_opts(m, mnt);

    /* Tagged fields ("foo:X" or "bar") */
    if (IS_MNT_SHARED(r))
        seq_printf(m, " shared:%i", r->mnt_group_id);
    if (IS_MNT_SLAVE(r)) {
        int master = r->mnt_master->mnt_group_id;
        int dom = get_dominating_id(r, &p->root);
        seq_printf(m, " master:%i", master);
        if (dom && dom != master)
            seq_printf(m, " propagate_from:%i", dom);
    }
    if (IS_MNT_UNBINDABLE(r))
        seq_puts(m, " unbindable");

    /* Filesystem specific data */
    seq_puts(m, " - ");
    show_type(m, sb);
    seq_putc(m, ' ');
    if (sb->s_op->show_devname)
        err = sb->s_op->show_devname(m, mnt->mnt_root);
    else
        mangle(m, r->mnt_devname ? r->mnt_devname : "none");
    if (err)
        goto out;
    seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
    err = show_sb_opts(m, sb);
    if (err)
        goto out;
    if (sb->s_op->show_options)
        err = sb->s_op->show_options(m, mnt->mnt_root);
    seq_putc(m, '\n');
out:
    return err;
}

static int show_vfsstat(struct seq_file *m, struct vfsmount *mnt)
{
    struct mount *r = real_mount(mnt);
    struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
    struct super_block *sb = mnt_path.dentry->d_sb;
    int err = 0;

    /* device */
    if (sb->s_op->show_devname) {
        seq_puts(m, "device ");
        err = sb->s_op->show_devname(m, mnt_path.dentry);
    } else {
        if (r->mnt_devname) {
            seq_puts(m, "device ");
            mangle(m, r->mnt_devname);
        } else
            seq_puts(m, "no device");
    }

    /* mount point */
    seq_puts(m, " mounted on ");
    seq_path(m, &mnt_path, " \t\n\\");
    seq_putc(m, ' ');

    /* file system type */
    seq_puts(m, "with fstype ");
    show_type(m, sb);

    /* optional statistics */
    if (sb->s_op->show_stats) {
        seq_putc(m, ' ');
        if (!err)
            err = sb->s_op->show_stats(m, mnt_path.dentry);
    }

    seq_putc(m, '\n');
    return err;
}

static int mounts_open_common(struct inode *inode, struct file *file,
                  int (*show)(struct seq_file *, struct vfsmount *))
{
    struct task_struct *task = get_proc_task(inode);
    struct nsproxy *nsp;
    struct mnt_namespace *ns = NULL;
    struct path root;
    struct proc_mounts *p;
    int ret = -EINVAL;

    if (!task)
        goto err;

    rcu_read_lock();
    nsp = task_nsproxy(task);
    if (!nsp) {
        rcu_read_unlock();
        put_task_struct(task);
        goto err;
    }
    ns = nsp->mnt_ns;
    if (!ns) {
        rcu_read_unlock();
        put_task_struct(task);
        goto err;
    }
    get_mnt_ns(ns);
    rcu_read_unlock();
    task_lock(task);
    if (!task->fs) {
        task_unlock(task);
        put_task_struct(task);
        ret = -ENOENT;
        goto err_put_ns;
    }
    get_fs_root(task->fs, &root);
    task_unlock(task);
    put_task_struct(task);

    ret = -ENOMEM;
    p = kmalloc(sizeof(struct proc_mounts), GFP_KERNEL);
    if (!p)
        goto err_put_path;

    file->private_data = &p->m;
    ret = seq_open(file, &mounts_op);
    if (ret)
        goto err_free;

    p->ns = ns;
    p->root = root;
    p->m.poll_event = ns->event;
    p->show = show;

    return 0;

 err_free:
    kfree(p);
 err_put_path:
    path_put(&root);
 err_put_ns:
    put_mnt_ns(ns);
 err:
    return ret;
}

static int mounts_release(struct inode *inode, struct file *file)
{
    struct proc_mounts *p = proc_mounts(file->private_data);
    path_put(&p->root);
    put_mnt_ns(p->ns);
    return seq_release(inode, file);
}

static int mounts_open(struct inode *inode, struct file *file)
{
    return mounts_open_common(inode, file, show_vfsmnt);
}

static int mountinfo_open(struct inode *inode, struct file *file)
{
    return mounts_open_common(inode, file, show_mountinfo);
}

static int mountstats_open(struct inode *inode, struct file *file)
{
    return mounts_open_common(inode, file, show_vfsstat);
}

const struct file_operations proc_mounts_operations = {
    .open       = mounts_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = mounts_release,
    .poll       = mounts_poll,
};

const struct file_operations proc_mountinfo_operations = {
    .open       = mountinfo_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = mounts_release,
    .poll       = mounts_poll,
};

const struct file_operations proc_mountstats_operations = {
    .open       = mountstats_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = mounts_release,
};