Unverified Commit 78aa08a8 authored by Christian Brauner's avatar Christian Brauner
Browse files

fs: add path_mounted() 



Add a small helper to check whether a path refers to the root of the
mount instead of open-coding this everywhere.

Reviewed-by: default avatarSeth Forshee (DigitalOcean) <sforshee@kernel.org>
Message-Id: <20230202-fs-move-mount-replace-v4-1-98f3d80d7eaa@kernel.org>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent f1fcbaa1

fs/namespace.c

+24 −12
Original line number Diff line number Diff line
@@ -1767,6 +1767,19 @@ bool may_mount(void) 
	return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);

}



/**

 * path_mounted - check whether path is mounted

 * @path: path to check

 *

 * Determine whether @path refers to the root of a mount.

 *

 * Return: true if @path is the root of a mount, false if not.

 */

static inline bool path_mounted(const struct path *path)

{

	return path->mnt->mnt_root == path->dentry;

}



static void warn_mandlock(void)

{

	pr_warn_once("=======================================================\n"
@@ -1782,7 +1795,7 @@ static int can_umount(const struct path *path, int flags) 


	if (!may_mount())

		return -EPERM;

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

	if (!path_mounted(path))

		return -EINVAL;

	if (!check_mnt(mnt))

		return -EINVAL;
@@ -2367,7 +2380,7 @@ static int do_change_type(struct path *path, int ms_flags) 
	int type;

	int err = 0;



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

	if (!path_mounted(path))

		return -EINVAL;



	type = flags_to_propagation_type(ms_flags);
@@ -2643,7 +2656,7 @@ static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags) 
	if (!check_mnt(mnt))

		return -EINVAL;



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

	if (!path_mounted(path))

		return -EINVAL;



	if (!can_change_locked_flags(mnt, mnt_flags))
@@ -2682,7 +2695,7 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, 
	if (!check_mnt(mnt))

		return -EINVAL;



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

	if (!path_mounted(path))

		return -EINVAL;



	if (!can_change_locked_flags(mnt, mnt_flags))
@@ -2772,9 +2785,9 @@ static int do_set_group(struct path *from_path, struct path *to_path) 


	err = -EINVAL;

	/* To and From paths should be mount roots */

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

	if (!path_mounted(from_path))

		goto out;

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

	if (!path_mounted(to_path))

		goto out;



	/* Setting sharing groups is only allowed across same superblock */
@@ -2855,7 +2868,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path) 
	if (old->mnt.mnt_flags & MNT_LOCKED)

		goto out;



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

	if (!path_mounted(old_path))

		goto out;



	if (d_is_dir(new_path->dentry) !=
@@ -2937,8 +2950,7 @@ static int do_add_mount(struct mount *newmnt, struct mountpoint *mp, 
	}



	/* Refuse the same filesystem on the same mount point */

	if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&

	    path->mnt->mnt_root == path->dentry)

	if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path_mounted(path))

		return -EBUSY;



	if (d_is_symlink(newmnt->mnt.mnt_root))
@@ -3917,11 +3929,11 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, 
	if (new_mnt == root_mnt || old_mnt == root_mnt)

		goto out4; /* loop, on the same file system  */

	error = -EINVAL;

	if (root.mnt->mnt_root != root.dentry)

	if (!path_mounted(&root))

		goto out4; /* not a mountpoint */

	if (!mnt_has_parent(root_mnt))

		goto out4; /* not attached */

	if (new.mnt->mnt_root != new.dentry)

	if (!path_mounted(&new))

		goto out4; /* not a mountpoint */

	if (!mnt_has_parent(new_mnt))

		goto out4; /* not attached */
@@ -4124,7 +4136,7 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) 
	struct mount *mnt = real_mount(path->mnt);

	int err = 0;



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

	if (!path_mounted(path))

		return -EINVAL;



	if (kattr->mnt_userns) {