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new predicate: anon_ns_root(mount) 

checks if mount is the root of an anonymouns namespace.
Switch open-coded equivalents to using it.

For mounts that belong to anon namespace !mnt_has_parent(mount)
is the same as mount == ns->root, and intent is more obvious in
the latter form.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2025-06-08 23:25:36 -04:00
parent e031251cb2
commit 05da054d43
2 changed files with 10 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
fs/mount.h
View File

@ -161,6 +161,13 @@ static inline bool is_anon_ns(struct mnt_namespace *ns)
return ns->seq == 0; return ns->seq == 0;
} }
static inline bool anon_ns_root(const struct mount *m)
{
struct mnt_namespace *ns = READ_ONCE(m->mnt_ns);
return !IS_ERR_OR_NULL(ns) && is_anon_ns(ns) && m == ns->root;
}
static inline bool mnt_ns_attached(const struct mount *mnt) static inline bool mnt_ns_attached(const struct mount *mnt)
{ {
return !RB_EMPTY_NODE(&mnt->mnt_node); return !RB_EMPTY_NODE(&mnt->mnt_node);

28
fs/namespace.c
View File

@ -2480,9 +2480,7 @@ struct vfsmount *clone_private_mount(const struct path *path)
* loops get created. * loops get created.
*/ */
if (!check_mnt(old_mnt)) { if (!check_mnt(old_mnt)) {
if (!is_mounted(&old_mnt->mnt) || if (!anon_ns_root(old_mnt))
!is_anon_ns(old_mnt->mnt_ns) ||
mnt_has_parent(old_mnt))
return ERR_PTR(-EINVAL); return ERR_PTR(-EINVAL);
if (!check_for_nsfs_mounts(old_mnt)) if (!check_for_nsfs_mounts(old_mnt))
@ -3649,9 +3647,6 @@ static int do_move_mount(struct path *old_path,
ns = old->mnt_ns; ns = old->mnt_ns;
err = -EINVAL; err = -EINVAL;
/* The thing moved must be mounted... */
if (!is_mounted(&old->mnt))
goto out;
if (check_mnt(old)) { if (check_mnt(old)) {
/* if the source is in our namespace... */ /* if the source is in our namespace... */
@ -3664,10 +3659,8 @@ static int do_move_mount(struct path *old_path,
} else { } else {
/* /*
* otherwise the source must be the root of some anon namespace. * otherwise the source must be the root of some anon namespace.
* AV: check for mount being root of an anon namespace is worth
* an inlined predicate...
*/ */
if (!is_anon_ns(ns) || mnt_has_parent(old)) if (!anon_ns_root(old))
goto out; goto out;
/* /*
* Bail out early if the target is within the same namespace - * Bail out early if the target is within the same namespace -
@ -5028,22 +5021,7 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
err = -EINVAL; err = -EINVAL;
lock_mount_hash(); lock_mount_hash();
/* Ensure that this isn't anything purely vfs internal. */ if (!anon_ns_root(mnt) && !check_mnt(mnt))
if (!is_mounted(&mnt->mnt))
goto out;
/*
* If this is an attached mount make sure it's located in the callers
* mount namespace. If it's not don't let the caller interact with it.
*
* If this mount doesn't have a parent it's most often simply a
* detached mount with an anonymous mount namespace. IOW, something
* that's simply not attached yet. But there are apparently also users
* that do change mount properties on the rootfs itself. That obviously
* neither has a parent nor is it a detached mount so we cannot
* unconditionally check for detached mounts.
*/
if ((mnt_has_parent(mnt) || !is_anon_ns(mnt->mnt_ns)) && !check_mnt(mnt))
goto out; goto out;
/* /*