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 C3D6CC678D4 for ; Thu, 2 Mar 2023 22:35:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230086AbjCBWfg (ORCPT ); Thu, 2 Mar 2023 17:35:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229633AbjCBWfg (ORCPT ); Thu, 2 Mar 2023 17:35:36 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AE9AD4C6F4; Thu, 2 Mar 2023 14:35:31 -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 3B933B811EF; Thu, 2 Mar 2023 22:35:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9FF6AC433EF; Thu, 2 Mar 2023 22:35:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1677796528; bh=tUyw0AY7oMULtmvxSFUaSnVpS+zW4iVINchd0EaRh4U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=QIgg/1/8lfJfG58syf+xFKaD7LhK1v3N5Ew2fWsoWX6ipNifRH58Ye+3X8oy99h8m K2v0YdVaYzxZFoI2NMgPOAEaBg59MXRAuTLz8TvEho1opDN10P91qLlhifF/bcRoKE I0jrUyi+FRiCWifIP30JNlwN1wQxppabrXysyi3MhbaXMKwfSSn1FI++KVQUElTu5r WyJM6ki4rur4sxAKnJluCF/wKsdszyDHKm8hTkPzJCZ6JwXL4s77I5SalGwkg/6wKr bcI7OzZmqrJOQTaTKX7QQ4qKXVRu6nYDf3OX7dcipVoV2bh7WeslZFbM0buiFuVDTd IDMOVtixM1esQ== Date: Thu, 2 Mar 2023 14:35:27 -0800 From: Jakub Kicinski To: Kees Cook Cc: Kees Cook , linux-hardening@vger.kernel.org, bpf@vger.kernel.org, "Joel Fernandes (Google)" Subject: Re: splat in ikheaders_read (bpftrace) Message-ID: <20230302143527.4bee6f7e@kernel.org> In-Reply-To: <20230302141231.2c0a3761@kernel.org> References: <20230302112130.6e402a98@kernel.org> <22EA7360-E2FC-4A23-BF0B-EFDE523F9605@kernel.org> <20230302140814.294aece0@kernel.org> <20230302141231.2c0a3761@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, 2 Mar 2023 14:12:31 -0800 Jakub Kicinski wrote: > On Thu, 2 Mar 2023 14:08:14 -0800 Jakub Kicinski wrote: > > Mm. Actually stopping to look at the code - I don't see it bound > > checking against kernel_headers_data_end :| Maybe we need: > >=20 > > @@ -34,6 +35,7 @@ ikheaders_read(struct file *file, struct kobject *ko= bj, > > struct bin_attribute *bin_attr, > > char *buf, loff_t off, size_t len) > > { > > + len =3D min_t(size_t, kernel_headers_data_end - kernel_headers_= data, len); > > memcpy(buf, &kernel_headers_data + off, len); > > return len; > > } =20 >=20 > Scratch that, the size is set at init time. > My guess was memcpy() thinks the size of kernel_headers_data > is 1 since it's declared as char? Like this? ---->8-------------------- =46rom 7549153017144281c2475d9370962ad4d0ea8d4c Mon Sep 17 00:00:00 2001 From: Jakub Kicinski Date: Thu, 2 Mar 2023 11:15:53 -0800 Subject: [PATCH] kheaders: use a flex array for the symbol Kernels with hardened copy hit: detected buffer overflow in memcpy kernel BUG at lib/string_helpers.c:1027! invalid opcode: 0000 [#8] SMP KASAN CPU: 1 PID: 1094 Comm: tar Tainted: G D 6.2.0-12879-g04= 0b4d2ce1ad #646 RIP: 0010:fortify_panic+0xf/0x20 [...] Call Trace: ikheaders_read+0x45/0x50 [kheaders] kernfs_fop_read_iter+0x1a4/0x2f0 Repro: $ cat /sys/kernel/kheaders.tar.xz >> /dev/null Fixes: 43d8ce9d65a5 ("Provide in-kernel headers to make extending kernel ea= sier") Signed-off-by: Jakub Kicinski --- kernel/kheaders.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/kheaders.c b/kernel/kheaders.c index 8f69772af77b..90562eb4093a 100644 --- a/kernel/kheaders.c +++ b/kernel/kheaders.c @@ -26,7 +26,7 @@ asm ( " .popsection \n" ); =20 -extern char kernel_headers_data; +extern char kernel_headers_data[]; extern char kernel_headers_data_end; =20 static ssize_t @@ -34,7 +34,7 @@ ikheaders_read(struct file *file, struct kobject *kobj, struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len) { - memcpy(buf, &kernel_headers_data + off, len); + memcpy(buf, &kernel_headers_data[off], len); return len; } =20 @@ -49,7 +49,7 @@ static struct bin_attribute kheaders_attr __ro_after_init= =3D { static int __init ikheaders_init(void) { kheaders_attr.size =3D (&kernel_headers_data_end - - &kernel_headers_data); + &kernel_headers_data[0]); return sysfs_create_bin_file(kernel_kobj, &kheaders_attr); } =20 --=20 2.39.2