// SPDX-License-Identifier: GPL-2.0
/*
 * 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 <linux/sched/task.h>

#include "proc/internal.h" /* only for get_proc_task() in ->open() */

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

static __poll_t mounts_poll(struct file *file, poll_table *wait)
{
        struct seq_file *m = file->private_data;
        struct proc_mounts *p = m->private;
        struct mnt_namespace *ns = p->ns;
        __poll_t res = EPOLLIN | EPOLLRDNORM;
        int event;

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

        event = READ_ONCE(ns->event);
        if (m->poll_event != event) {
                m->poll_event = event;
                res |= EPOLLERR | EPOLLPRI;
        }

        return res;
}

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

static int show_sb_opts(struct seq_file *m, struct super_block *sb)
{
        static const struct proc_fs_opts fs_opts[] = {
                { SB_SYNCHRONOUS, ",sync" },
                { SB_DIRSYNC, ",dirsync" },
                { SB_MANDLOCK, ",mand" },
                { SB_LAZYTIME, ",lazytime" },
                { 0, NULL }
        };
        const struct proc_fs_opts *fs_infop;

        for (fs_infop = fs_opts; 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_vfsmnt_opts(struct seq_file *m, struct vfsmount *mnt)
{
        static const struct proc_fs_opts mnt_opts[] = {
                { MNT_NOSUID, ",nosuid" },
                { MNT_NODEV, ",nodev" },
                { MNT_NOEXEC, ",noexec" },
                { MNT_NOATIME, ",noatime" },
                { MNT_NODIRATIME, ",nodiratime" },
                { MNT_RELATIME, ",relatime" },
                { MNT_NOSYMFOLLOW, ",nosymfollow" },
                { 0, NULL }
        };
        const struct proc_fs_opts *fs_infop;

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

        if (is_idmapped_mnt(mnt))
                seq_puts(m, ",idmapped");
}

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) {
                seq_putc(m, '.');
                mangle(m, sb->s_subtype);
        }
}

static int show_vfsmnt(struct seq_file *m, struct vfsmount *mnt)
{
        struct proc_mounts *p = m->private;
        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;

        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);
        }
        seq_putc(m, ' ');
        /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
        err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
        if (err)
                goto out;
        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_vfsmnt_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 = m->private;
        struct mount *r = real_mount(mnt);
        struct super_block *sb = mnt->mnt_sb;
        struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
        int err;

        seq_printf(m, "%i %i %u:%u ", r->mnt_id, r->mnt_parent->mnt_id,
                   MAJOR(sb->s_dev), MINOR(sb->s_dev));
        err = show_path(m, mnt->mnt_root);
        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, &p->root, " \t\n\\");
        if (err)
                goto out;

        seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw");
        show_vfsmnt_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);
                if (err)
                        goto out;
        } else {
                mangle(m, r->mnt_devname);
        }
        seq_puts(m, sb_rdonly(sb) ? " 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 proc_mounts *p = m->private;
        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;

        /* device */
        seq_puts(m, "device ");
        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);
        }

        /* mount point */
        seq_puts(m, " mounted on ");
        /* mountpoints outside of chroot jail will give SEQ_SKIP on this */
        err = seq_path_root(m, &mnt_path, &p->root, " \t\n\\");
        if (err)
                goto out;
        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, ' ');
                err = sb->s_op->show_stats(m, mnt_path.dentry);
        }

        seq_putc(m, '\n');
out:
        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;
        struct seq_file *m;
        int ret = -EINVAL;

        if (!task)
                goto err;

        task_lock(task);
        nsp = task->nsproxy;
        if (!nsp || !nsp->mnt_ns) {
                task_unlock(task);
                put_task_struct(task);
                goto err;
        }
        ns = nsp->mnt_ns;
        get_mnt_ns(ns);
        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 = seq_open_private(file, &mounts_op, sizeof(struct proc_mounts));
        if (ret)
                goto err_put_path;

        m = file->private_data;
        m->poll_event = ns->event;

        p = m->private;
        p->ns = ns;
        p->root = root;
        p->show = show;

        return 0;

 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 seq_file *m = file->private_data;
        struct proc_mounts *p = m->private;
        path_put(&p->root);
        put_mnt_ns(p->ns);
        return seq_release_private(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_iter      = seq_read_iter,
        .splice_read    = copy_splice_read,
        .llseek         = seq_lseek,
        .release        = mounts_release,
        .poll           = mounts_poll,
};

const struct file_operations proc_mountinfo_operations = {
        .open           = mountinfo_open,
        .read_iter      = seq_read_iter,
        .splice_read    = copy_splice_read,
        .llseek         = seq_lseek,
        .release        = mounts_release,
        .poll           = mounts_poll,
};

const struct file_operations proc_mountstats_operations = {
        .open           = mountstats_open,
        .read_iter      = seq_read_iter,
        .splice_read    = copy_splice_read,
        .llseek         = seq_lseek,
        .release        = mounts_release,
};