From: Christian Brauner <brauner@kernel.org>
Date: Wed, 16 Oct 2024 17:49:48 +0000 (+0200)
Subject: fs: don't try and remove empty rbtree node
X-Git-Tag: v6.11.6~46
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a8b155a2c30dc9a5ba837aa5fcba9a47cc031a9b;p=thirdparty%2Fkernel%2Fstable.git

fs: don't try and remove empty rbtree node

commit 229fd15908fe1f99b1de4cde3326e62d1e892611 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 155c6abda71da..666070457cf74 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3917,7 +3917,9 @@ 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) {