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 6E7A9C3DA7D for ; Wed, 4 Jan 2023 00:55:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238892AbjADAzC (ORCPT ); Tue, 3 Jan 2023 19:55:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229685AbjADAzB (ORCPT ); Tue, 3 Jan 2023 19:55:01 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F114817070; Tue, 3 Jan 2023 16:54:59 -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 ams.source.kernel.org (Postfix) with ESMTPS id A2345B81151; Wed, 4 Jan 2023 00:54:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2880FC433EF; Wed, 4 Jan 2023 00:54:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1672793697; bh=D6kfiVE9mOojgtBjsTsllPEN/tZ8Ks/6aaCN32Ve4Fs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kCCVcy5Fg8yE5P4F1SSVrZau28sxHVJfMQmJm5uNuMn/euAdc62ttf8L99nhGl3Hr iYfz3N/vZW+pLgKR2GEt+em3gmFkUTDCtFCAcgeo0iH5ZLYVF3OW1pbxUg75MuI1uS PrZkTO6NXSz94VPxNC3E7Jc0rGW4MRPb4E6d4H5ReZrW+sGjZ3MwwbVLZDAFWSl7az ux9pKObnTpv5WmqH/qNVHjm+nQ0QLPU58CQ1UoME7IIDSTKZlTvj5soX7TSuqUmZZK yqtkR/Q+VXo0kwutDlKWcKn7qboODjjJWSmifteSat3rxTFdyKwosfOP3APthscdqS wMtIttSbc2kvA== Date: Tue, 3 Jan 2023 18:55:01 -0600 From: "Gustavo A. R. Silva" 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 Build-tested-by: Gustavo A. R. Silva Reviewed-by: Gustavo A. R. Silva Just for the record, this is the warning Clang reports without this patch: fs/ext4/sysfs.c:508:13: warning: cast from 'void (*)(const void *)' to 'void (*)(struct kobject *)' converts to incompatible function type [-Wcast-function-type-strict] Thanks -- Gustavo > --- > 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, > }; > > void ext4_notify_error_sysfs(struct ext4_sb_info *sbi) > -- > 2.34.1 >