fs: don't try and remove empty rbtree node

When copying a namespace we won't have added the new copy into the
namespace rbtree until after the copy succeeded. Calling free_mnt_ns()
will try to remove the copy from the rbtree which is invalid. Simply
free the namespace skeleton directly.

Link: https://lore.kernel.org/r/20241016-adapter-seilwinde-83c508a7bde1@brauner
Fixes: 1901c92497bd ("fs: keep an index of current mount namespaces")
Tested-by: Brad Spengler <spender@grsecurity.net>
Cc: stable@vger.kernel.org # v6.11+
Reported-by: Brad Spengler <spender@grsecurity.net>
Suggested-by: Brad Spengler <spender@grsecurity.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/namespace.c b/fs/namespace.c
index 93c3778..d26f5e6 100644 (file)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3944,7 +3944,9 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
        new = copy_tree(old, old->mnt.mnt_root, copy_flags);
        if (IS_ERR(new)) {
                namespace_unlock();
-               free_mnt_ns(new_ns);
+               ns_free_inum(&new_ns->ns);
+               dec_mnt_namespaces(new_ns->ucounts);
+               mnt_ns_release(new_ns);
                return ERR_CAST(new);
        }
        if (user_ns != ns->user_ns) {