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[209.132.180.67]) by mx.google.com with ESMTP id n9si26907310pgj.171.2019.07.29.12.55.43; Mon, 29 Jul 2019 12:55:43 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=pHJCkmnX; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404223AbfG2Tzl (ORCPT + 29 others); Mon, 29 Jul 2019 15:55:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:48466 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391047AbfG2Tzi (ORCPT ); Mon, 29 Jul 2019 15:55:38 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E62C2204EC; Mon, 29 Jul 2019 19:55:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564430137; bh=T2jjRL4C0aJe4QicyVoBE1EXvP3PYDkgBDX+2pELYFA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pHJCkmnXXCETsgb65XnfDzFMr0PVuZcJpkGGo4i74OcWM069VSU33/dCTvwc1Hy8A pyOIXpdCDvGCinvBMTolzsix5fCpsYxfBDFwx1HWusf5Kx5guRh4SnN9/EnxOT3SG9 qYzdZUEadLL6ewJn2MeqUvcFF1fZ1uF9FHJooLLw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Arnd Bergmann , Kees Cook Subject: [PATCH 5.2 209/215] structleak: disable STRUCTLEAK_BYREF in combination with KASAN_STACK Date: Mon, 29 Jul 2019 21:23:25 +0200 Message-Id: <20190729190816.215884327@linuxfoundation.org> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190729190739.971253303@linuxfoundation.org> References: <20190729190739.971253303@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Arnd Bergmann commit 173e6ee21e2b3f477f07548a79c43b8d9cfbb37d upstream. The combination of KASAN_STACK and GCC_PLUGIN_STRUCTLEAK_BYREF leads to much larger kernel stack usage, as seen from the warnings about functions that now exceed the 2048 byte limit: drivers/media/i2c/tvp5150.c:253:1: error: the frame size of 3936 bytes is larger than 2048 bytes drivers/media/tuners/r820t.c:1327:1: error: the frame size of 2816 bytes is larger than 2048 bytes drivers/net/wireless/broadcom/brcm80211/brcmsmac/phy/phy_n.c:16552:1: error: the frame size of 3144 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] fs/ocfs2/aops.c:1892:1: error: the frame size of 2088 bytes is larger than 2048 bytes fs/ocfs2/dlm/dlmrecovery.c:737:1: error: the frame size of 2088 bytes is larger than 2048 bytes fs/ocfs2/namei.c:1677:1: error: the frame size of 2584 bytes is larger than 2048 bytes fs/ocfs2/super.c:1186:1: error: the frame size of 2640 bytes is larger than 2048 bytes fs/ocfs2/xattr.c:3678:1: error: the frame size of 2176 bytes is larger than 2048 bytes net/bluetooth/l2cap_core.c:7056:1: error: the frame size of 2144 bytes is larger than 2048 bytes [-Werror=frame-larger-than=] net/bluetooth/l2cap_core.c: In function 'l2cap_recv_frame': net/bridge/br_netlink.c:1505:1: error: the frame size of 2448 bytes is larger than 2048 bytes net/ieee802154/nl802154.c:548:1: error: the frame size of 2232 bytes is larger than 2048 bytes net/wireless/nl80211.c:1726:1: error: the frame size of 2224 bytes is larger than 2048 bytes net/wireless/nl80211.c:2357:1: error: the frame size of 4584 bytes is larger than 2048 bytes net/wireless/nl80211.c:5108:1: error: the frame size of 2760 bytes is larger than 2048 bytes net/wireless/nl80211.c:6472:1: error: the frame size of 2112 bytes is larger than 2048 bytes The structleak plugin was previously disabled for CONFIG_COMPILE_TEST, but meant we missed some bugs, so this time we should address them. The frame size warnings are distracting, and risking a kernel stack overflow is generally not beneficial to performance, so it may be best to disallow that particular combination. This can be done by turning off either one. I picked the dependency in GCC_PLUGIN_STRUCTLEAK_BYREF and GCC_PLUGIN_STRUCTLEAK_BYREF_ALL, as this option is designed to make uninitialized stack usage less harmful when enabled on its own, but it also prevents KASAN from detecting those cases in which it was in fact needed. KASAN_STACK is currently implied by KASAN on gcc, but could be made a user selectable option if we want to allow combining (non-stack) KASAN with GCC_PLUGIN_STRUCTLEAK_BYREF. Note that it would be possible to specifically address the files that print the warning, but presumably the overall stack usage is still significantly higher than in other configurations, so this would not address the full problem. I could not test this with CONFIG_INIT_STACK_ALL, which may or may not suffer from a similar problem. Fixes: 81a56f6dcd20 ("gcc-plugins: structleak: Generalize to all variable types") Signed-off-by: Arnd Bergmann Link: https://lore.kernel.org/r/20190722114134.3123901-1-arnd@arndb.de Signed-off-by: Kees Cook Signed-off-by: Greg Kroah-Hartman --- security/Kconfig.hardening | 7 +++++++ 1 file changed, 7 insertions(+) --- a/security/Kconfig.hardening +++ b/security/Kconfig.hardening @@ -61,6 +61,7 @@ choice config GCC_PLUGIN_STRUCTLEAK_BYREF bool "zero-init structs passed by reference (strong)" depends on GCC_PLUGINS + depends on !(KASAN && KASAN_STACK=1) select GCC_PLUGIN_STRUCTLEAK help Zero-initialize any structures on the stack that may @@ -70,9 +71,15 @@ choice exposures, like CVE-2017-1000410: https://git.kernel.org/linus/06e7e776ca4d3654 + As a side-effect, this keeps a lot of variables on the + stack that can otherwise be optimized out, so combining + this with CONFIG_KASAN_STACK can lead to a stack overflow + and is disallowed. + config GCC_PLUGIN_STRUCTLEAK_BYREF_ALL bool "zero-init anything passed by reference (very strong)" depends on GCC_PLUGINS + depends on !(KASAN && KASAN_STACK=1) select GCC_PLUGIN_STRUCTLEAK help Zero-initialize any stack variables that may be passed