do_move_mount(): use the parent mount returned by do_lock_mount()

After successful do_lock_mount() call, mp.parent is set to either
real_mount(path->mnt) (for !beneath case) or to ->mnt_parent of that
(for beneath).  p is set to real_mount(path->mnt) and after
several uses it's made equal to mp.parent.  All uses prior to that
care only about p->mnt_ns and since p->mnt_ns == parent->mnt_ns,
we might as well use mp.parent all along.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/namespace.c b/fs/namespace.c
index a6f48750536ab25e0ec477c694ef7e4bc37226dc..bae4be8c7192a45bca8fb67d1b85c6101ff349db 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3566,7 +3566,6 @@ static inline bool may_use_mount(struct mount *mnt)
 static int do_move_mount(struct path *old_path,
                         struct path *new_path, enum mnt_tree_flags_t flags)
 {
-       struct mount *p;
        struct mount *old = real_mount(old_path->mnt);
        int err;
        bool beneath = flags & MNT_TREE_BENEATH;
@@ -3581,8 +3580,6 @@ static int do_move_mount(struct path *old_path,
        if (IS_ERR(mp.parent))
                return PTR_ERR(mp.parent);
 
-       p = real_mount(new_path->mnt);
-
        if (check_mnt(old)) {
                /* if the source is in our namespace... */
                /* ... it should be detachable from parent */
@@ -3592,7 +3589,7 @@ static int do_move_mount(struct path *old_path,
                if (IS_MNT_SHARED(old->mnt_parent))
                        return -EINVAL;
                /* ... and the target should be in our namespace */
-               if (!check_mnt(p))
+               if (!check_mnt(mp.parent))
                        return -EINVAL;
        } else {
                /*
@@ -3605,13 +3602,13 @@ static int do_move_mount(struct path *old_path,
                 * subsequent checks would've rejected that, but they lose
                 * some corner cases if we check it early.
                 */
-               if (old->mnt_ns == p->mnt_ns)
+               if (old->mnt_ns == mp.parent->mnt_ns)
                        return -EINVAL;
                /*
                 * Target should be either in our namespace or in an acceptable
                 * anon namespace, sensu check_anonymous_mnt().
                 */
-               if (!may_use_mount(p))
+               if (!may_use_mount(mp.parent))
                        return -EINVAL;
        }
 
@@ -3619,22 +3616,20 @@ static int do_move_mount(struct path *old_path,
                err = can_move_mount_beneath(old, new_path, mp.mp);
                if (err)
                        return err;
-
-               p = p->mnt_parent;
        }
 
        /*
         * Don't move a mount tree containing unbindable mounts to a destination
         * mount which is shared.
         */
-       if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
+       if (IS_MNT_SHARED(mp.parent) && tree_contains_unbindable(old))
                return -EINVAL;
        if (!check_for_nsfs_mounts(old))
                return -ELOOP;
-       if (mount_is_ancestor(old, p))
+       if (mount_is_ancestor(old, mp.parent))
                return -ELOOP;
 
-       return attach_recursive_mnt(old, p, mp.mp);
+       return attach_recursive_mnt(old, mp.parent, mp.mp);
 }
 
 static int do_move_mount_old(struct path *path, const char *old_name)