From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9709AC4708E for ; Wed, 4 Jan 2023 00:23:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233905AbjADAXt (ORCPT ); Tue, 3 Jan 2023 19:23:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229957AbjADAXr (ORCPT ); Tue, 3 Jan 2023 19:23:47 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 630F7164B8; Tue, 3 Jan 2023 16:23:47 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id EF72961560; Wed, 4 Jan 2023 00:23:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 310C8C433D2; Wed, 4 Jan 2023 00:23:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1672791826; bh=Ub1O4ARA4Fg1QerVBHMPex3kBs1tuOPd9OUWy+AyaE8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=OZwcaB7pDsRLazyUJiUCwgCbXeXHfPdPlBxzS9RGiCSHj9KgfXl7IbIbWALJzQfsQ XacyMUuuQrCcLhrYdplLErkyezbqno6aB4dGt9WzbC/zMfQbEjIH/jEhx0wCYhILHw 842OZZRWeHYTnWl5/K7R7xf56w9baqfnSzZQsAQwcdfvoJ0i9b6lO7ET0WCYayim8f EWbh/u1kI/ghzkRHK+x970ganXbmY08478lfgqX5/6OZpuVLzqvGOdrXpsGoktvjN5 yg0qacQjxBYYYzgnG4OXJ1qwQHYLHvlhB3osx9zyRGNN+JoawlYRvzHHIQHTH5MQnE ySiN15/1QoAoQ== Date: Wed, 4 Jan 2023 00:23:44 +0000 From: Eric Biggers To: Kees Cook Cc: tytso@mit.edu, Andreas Dilger , Nathan Chancellor , Nick Desaulniers , Tom Rix , linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, llvm@lists.linux.dev, linux-hardening@vger.kernel.org Subject: Re: [PATCH] ext4: Fix function prototype mismatch for ext4_feat_ktype Message-ID: References: <20230103234616.never.915-kees@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230103234616.never.915-kees@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Tue, Jan 03, 2023 at 03:46:20PM -0800, Kees Cook wrote: > With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), > indirect call targets are validated against the expected function > pointer prototype to make sure the call target is valid to help mitigate > ROP attacks. If they are not identical, there is a failure at run time, > which manifests as either a kernel panic or thread getting killed. > > ext4_feat_ktype was setting the "release" handler to "kfree", which > doesn't have a matching function prototype. Add a simple wrapper > with the correct prototype. > > This was found as a result of Clang's new -Wcast-function-type-strict > flag, which is more sensitive than the simpler -Wcast-function-type, > which only checks for type width mismatches. > > Signed-off-by: Kees Cook > --- > fs/ext4/sysfs.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c > index d233c24ea342..83cf8b5afb54 100644 > --- a/fs/ext4/sysfs.c > +++ b/fs/ext4/sysfs.c > @@ -491,6 +491,11 @@ static void ext4_sb_release(struct kobject *kobj) > complete(&sbi->s_kobj_unregister); > } > > +static void ext4_kobject_release(struct kobject *kobj) > +{ > + kfree(kobj); > +} > + > static const struct sysfs_ops ext4_attr_ops = { > .show = ext4_attr_show, > .store = ext4_attr_store, > @@ -505,7 +510,7 @@ static struct kobj_type ext4_sb_ktype = { > static struct kobj_type ext4_feat_ktype = { > .default_groups = ext4_feat_groups, > .sysfs_ops = &ext4_attr_ops, > - .release = (void (*)(struct kobject *))kfree, > + .release = ext4_kobject_release, For consistency, maybe call this ext4_feat_release? So ext4_sb_ktype would have ext4_sb_release, and ext4_feat_ktype would have ext4_feat_release. I'm also surprised that this wasn't found earlier. Is it possible that CFI does not actually distinguish between the two function prototypes here? - Eric