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Commit 57eccb83 authored by Al Viro's avatar Al Viro
Browse files

mount: consolidate permission checks 



... and ask for global CAP_SYS_ADMIN only for superblock-level remounts

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 9b40bc90

fs/namespace.c

+7 −33
Original line number Original line Diff line number Diff line
@@ -1300,24 +1300,6 @@ SYSCALL_DEFINE1(oldumount, char __user *, name) 




#endif

#endif





static int mount_is_safe(struct path *path)

{

	if (may_mount())

		return 0;

	return -EPERM;

#ifdef notyet

	if (S_ISLNK(path->dentry->d_inode->i_mode))

		return -EPERM;

	if (path->dentry->d_inode->i_mode & S_ISVTX) {

		if (current_uid() != path->dentry->d_inode->i_uid)

			return -EPERM;

	}

	if (inode_permission(path->dentry->d_inode, MAY_WRITE))

		return -EPERM;

	return 0;

#endif

}



static bool mnt_ns_loop(struct path *path)

static bool mnt_ns_loop(struct path *path)

{

{

	/* Could bind mounting the mount namespace inode cause a

	/* Could bind mounting the mount namespace inode cause a
@@ -1640,9 +1622,6 @@ static int do_change_type(struct path *path, int flag) 
	int type;

	int type;

	int err = 0;

	int err = 0;





	if (!may_mount())

		return -EPERM;



	if (path->dentry != path->mnt->mnt_root)

	if (path->dentry != path->mnt->mnt_root)

		return -EINVAL;

		return -EINVAL;
@@ -1676,9 +1655,7 @@ static int do_loopback(struct path *path, const char *old_name, 
	LIST_HEAD(umount_list);

	LIST_HEAD(umount_list);

	struct path old_path;

	struct path old_path;

	struct mount *mnt = NULL, *old;

	struct mount *mnt = NULL, *old;

	int err = mount_is_safe(path);

	int err;

	if (err)

		return err;

	if (!old_name || !*old_name)

	if (!old_name || !*old_name)

		return -EINVAL;

		return -EINVAL;

	err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);

	err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
@@ -1755,9 +1732,6 @@ static int do_remount(struct path *path, int flags, int mnt_flags, 
	struct super_block *sb = path->mnt->mnt_sb;

	struct super_block *sb = path->mnt->mnt_sb;

	struct mount *mnt = real_mount(path->mnt);

	struct mount *mnt = real_mount(path->mnt);





	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	if (!check_mnt(mnt))

	if (!check_mnt(mnt))

		return -EINVAL;

		return -EINVAL;
@@ -1771,6 +1745,8 @@ static int do_remount(struct path *path, int flags, int mnt_flags, 
	down_write(&sb->s_umount);

	down_write(&sb->s_umount);

	if (flags & MS_BIND)

	if (flags & MS_BIND)

		err = change_mount_flags(path->mnt, flags);

		err = change_mount_flags(path->mnt, flags);

	else if (!capable(CAP_SYS_ADMIN))

		err = -EPERM;

	else

	else

		err = do_remount_sb(sb, flags, data, 0);

		err = do_remount_sb(sb, flags, data, 0);

	if (!err) {

	if (!err) {
@@ -1803,9 +1779,7 @@ static int do_move_mount(struct path *path, const char *old_name) 
	struct path old_path, parent_path;

	struct path old_path, parent_path;

	struct mount *p;

	struct mount *p;

	struct mount *old;

	struct mount *old;

	int err = 0;

	int err;

	if (!may_mount())

		return -EPERM;

	if (!old_name || !*old_name)

	if (!old_name || !*old_name)

		return -EINVAL;

		return -EINVAL;

	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);

	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
@@ -1947,9 +1921,6 @@ static int do_new_mount(struct path *path, const char *fstype, int flags, 
	if (!fstype)

	if (!fstype)

		return -EINVAL;

		return -EINVAL;





	if (!may_mount())

		return -EPERM;



	type = get_fs_type(fstype);

	type = get_fs_type(fstype);

	if (!type)

	if (!type)

		return -ENODEV;

		return -ENODEV;
@@ -2263,6 +2234,9 @@ long do_mount(const char *dev_name, const char *dir_name, 
	if (retval)

	if (retval)

		goto dput_out;

		goto dput_out;





	if (!may_mount())

		return -EPERM;



	/* Default to relatime unless overriden */

	/* Default to relatime unless overriden */

	if (!(flags & MS_NOATIME))

	if (!(flags & MS_NOATIME))

		mnt_flags |= MNT_RELATIME;

		mnt_flags |= MNT_RELATIME;