From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C02A38F253; Sat, 17 Oct 2026 16:06:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792253215; cv=none; b=UPI7TJLLzHkhKclKF3N0l79S2IvreOQ5TE1beWq3g+W++fKYG3fxpllJtfzzgrb3ZxHB9DmmIIERwZL7q5DMj94YGf0JETshJ3Pg+4U8YDzRrVlwQqrYqAB9u2+szRZs6SS52RiYELhu4BTlJe6iDeBH8Yy1I5DiOn3zQn0Z1rw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792253215; c=relaxed/simple; bh=58El7vIF4mnaYQGZ2BxXDiojevhhPEc4KM4OCPQ9MZY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=awI6nO15hbcOFpFuEVrDbjDkZpUxvHMzj/sgNMp7uuMtgyYTwSANxXHptbyo3ZmuULsFDX6NIb1HbjbB4Z6EGX4KixYYnOE7T8Ud6ADcTMtbfFZKg9ori8IGBAHe08EQc2H1NV2CI+qQ1shAH4HtdO7FwXUem/AAvKLzLupIW20= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Mk423AVx; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Mk423AVx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4F8191F000C4; Sat, 17 Oct 2026 16:06:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792253213; bh=VNdvXQ/ng3Jtl9oZa4QhAPdlUFOtlDRyDr9Br0DviHs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Mk423AVx3tTgvvcu/CtY0i71HnNHJhsiN3MXf8qQNz6BWfpY30KJ5q0ST/SQxROsk f59RJicsAbtIo0MkoOnzVKJ8xc/0TU4sB3W5ewRgfIyQ61ZGbNIdfyvaSJ7UXyltN2 SINXYl/EzPjY4sE3j0twBLQYF44wBS9R30juESp8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Christian Brauner (Amutable)" , Sasha Levin Subject: [PATCH 6.12 046/869] namespace: check the target before walking it in do_mount_setattr() Date: Sat, 17 Oct 2026 17:48:07 +0200 Message-ID: <20261017160038.197518673@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160036.979869304@linuxfoundation.org> References: <20261017160036.979869304@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Christian Brauner [ Upstream commit 08f4288a37ef4b3d19b4a9599ec3048219cac828 ] When mount_setattr() changes the propagation type to MS_SHARED do_mount_setattr() takes namespace_sem and calls invent_group_ids() which walks the whole target tree with next_mnt() and allocates a peer group id for every mount that doesn't have one. Whether the caller may touch the target at all is only checked afterwards under mount_lock. If it may not, cleanup_group_ids() walks the tree a second time on the way out to free the ids again. A detached tree that a file descriptor keeps alive, a mount in another mount namespace or a mount below the root of an anonymous mount namespace does a bunch of allocation work that is completely useless because it will fail and revert right after. Do the right thing and check the target right after taking namespace_sem instead. A mount leaves its namespace only under namespace_sem so the mount stays stable. The check under mount_lock stays for the case where no propagation change is requested and namespace_sem isn't taken. Callers get the same EINVAL as before. Fixes: 2a1867219c7b ("fs: add mount_setattr()") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260926-work-mount-fixes-2-v1-5-f357abf3d17b@kernel.org Signed-off-by: Christian Brauner (Amutable) [ sashal: Replaced unavailable anon_ns_root() with equivalent checks using existing mount and namespace helpers. ] Signed-off-by: Sasha Levin --- fs/namespace.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/namespace.c b/fs/namespace.c index 5cfceae507098..808a8e79a4863 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -4721,6 +4721,13 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) * propagation. */ namespace_lock(); + /* invent_group_ids() walks the tree, only walk a mounted one */ + if (!is_mounted(&mnt->mnt) || + ((mnt_has_parent(mnt) || !is_anon_ns(mnt->mnt_ns)) && + !check_mnt(mnt))) { + namespace_unlock(); + return -EINVAL; + } if (kattr->propagation == MS_SHARED) { err = invent_group_ids(mnt, kattr->recurse); if (err) { @@ -4733,6 +4740,7 @@ static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) err = -EINVAL; lock_mount_hash(); + /* Checked under namespace_sem already if the propagation changes. */ /* Ensure that this isn't anything purely vfs internal. */ if (!is_mounted(&mnt->mnt)) goto out; -- 2.53.0