fs/proc_namespace.c - linux - Git at Google

 // 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_mnt_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);
 	}
 }

 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 ? r->mnt_devname : "none");
 	}
 	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_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 = 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));
 	if (sb->s_op->show_path) {
 		err = sb->s_op->show_path(m, mnt->mnt_root);
 		if (err)
 			goto out;
 	} else {
 		seq_dentry(m, mnt->mnt_root, " \t\n\\");
 	}
 	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_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);
 		if (err)
 			goto out;
 	} else {
 		mangle(m, r->mnt_devname ? r->mnt_devname : "none");
 	}
 	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 */
 	if (sb->s_op->show_devname) {
 		seq_puts(m, "device ");
 		err = sb->s_op->show_devname(m, mnt_path.dentry);
 		if (err)
 			goto out;
 	} 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 ");
 	/* 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;
 	INIT_LIST_HEAD(&p->cursor.mnt_list);
 	p->cursor.mnt.mnt_flags = MNT_CURSOR;

 	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);
 	mnt_cursor_del(p->ns, &p->cursor);
 	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	= generic_file_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	= generic_file_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	= generic_file_splice_read,
 	.llseek		= seq_lseek,
 	.release	= mounts_release,
 };
	// 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_mnt_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);
	}
	}

	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 ? r->mnt_devname : "none");
	}
	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_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 = 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));
	if (sb->s_op->show_path) {
	err = sb->s_op->show_path(m, mnt->mnt_root);
	if (err)
	goto out;
	} else {
	seq_dentry(m, mnt->mnt_root, " \t\n\\");
	}
	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_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);
	if (err)
	goto out;
	} else {
	mangle(m, r->mnt_devname ? r->mnt_devname : "none");
	}
	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 */
	if (sb->s_op->show_devname) {
	seq_puts(m, "device ");
	err = sb->s_op->show_devname(m, mnt_path.dentry);
	if (err)
	goto out;
	} 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 ");
	/* 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;
	INIT_LIST_HEAD(&p->cursor.mnt_list);
	p->cursor.mnt.mnt_flags = MNT_CURSOR;

	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);
	mnt_cursor_del(p->ns, &p->cursor);
	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 = generic_file_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 = generic_file_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 = generic_file_splice_read,
	.llseek = seq_lseek,
	.release = mounts_release,
	};