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[v2,28/63] fortify: Explicitly disable Clang support

Message ID	20210818060533.3569517-29-keescook@chromium.org
State	New
Headers	show Return-Path: <linux-wireless-owner@kernel.org> From: Kees Cook <keescook@chromium.org> To: linux-kernel@vger.kernel.org Cc: Kees Cook <keescook@chromium.org>, "Gustavo A. R. Silva" <gustavoars@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Andrew Morton <akpm@linux-foundation.org>, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com, Rasmus Villemoes <linux@rasmusvillemoes.dk>, linux-hardening@vger.kernel.org Subject: [PATCH v2 28/63] fortify: Explicitly disable Clang support Date: Tue, 17 Aug 2021 23:04:58 -0700 Message-Id: <20210818060533.3569517-29-keescook@chromium.org> In-Reply-To: <20210818060533.3569517-1-keescook@chromium.org> References: <20210818060533.3569517-1-keescook@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	Introduce strict memcpy() bounds checking \| expand [v2,00/63] Introduce strict memcpy() bounds checking [v2,04/63] pcmcia: ray_cs: Split memcpy() to avoid bounds check warning [v2,05/63] stddef: Introduce struct_group() helper macro [v2,07/63] skbuff: Switch structure bounds to struct_group() [v2,08/63] bnxt_en: Use struct_group_attr() for memcpy() region [v2,12/63] thermal: intel: int340x_thermal: Use struct_group() for memcpy() region [v2,13/63] iommu/amd: Use struct_group() for memcpy() region [v2,15/63] intersil: Use struct_group() for memcpy() region [v2,17/63] bnx2x: Use struct_group() for memcpy() region [v2,18/63] drm/amd/pm: Use struct_group() for memcpy() region [v2,21/63] net/mlx5e: Use struct_group() for memcpy() region [v2,23/63] media: omap3isp: Use struct_group() for memcpy() region [v2,26/63] lib/string: Move helper functions out of string.c [v2,27/63] fortify: Move remaining fortify helpers into fortify-string.h [v2,28/63] fortify: Explicitly disable Clang support [v2,31/63] fortify: Allow strlen() and strnlen() to pass compile-time known lengths [v2,34/63] fortify: Detect struct member overflows in memcpy() at compile-time [v2,37/63] string.h: Introduce memset_after() for wiping trailing members/padding [v2,38/63] xfrm: Use memset_after() to clear padding [v2,40/63] netfilter: conntrack: Use memset_startat() to zero struct nf_conn [v2,41/63] net: 802: Use memset_startat() to clear struct fields [v2,42/63] net: dccp: Use memset_startat() for TP zeroing [v2,44/63] mac80211: Use memset_after() to clear tx status [v2,45/63] ath11k: Use memset_startat() for clearing queue descriptors [v2,47/63] intel_th: msu: Use memset_startat() for clearing hw header [v2,48/63] IB/mthca: Use memset_startat() for clearing mpt_entry [v2,49/63] btrfs: Use memset_startat() to clear end of struct [v2,52/63] cm4000_cs: Use struct_group() to zero struct cm4000_dev region [v2,55/63] HID: roccat: Use struct_group() to zero kone_mouse_event [v2,58/63] ethtool: stats: Use struct_group() to clear all stats at once [v2,60/63] net/af_iucv: Use struct_group() to zero struct iucv_sock region [v2,61/63] powerpc: Split memset() to avoid multi-field overflow

Commit Message

Kees Cook Aug. 18, 2021, 6:04 a.m. UTC

Clang has never correctly compiled the FORTIFY_SOURCE defenses due to
a couple bugs:

	Eliding inlines with matching __builtin_* names
	https://bugs.llvm.org/show_bug.cgi?id=50322

	Incorrect __builtin_constant_p() of some globals
	https://bugs.llvm.org/show_bug.cgi?id=41459

In the process of making improvements to the FORTIFY_SOURCE defenses, the
first (silent) bug (coincidentally) becomes worked around, but exposes
the latter which breaks the build. As such, Clang must not be used with
CONFIG_FORTIFY_SOURCE until at least latter bug is fixed (in Clang 13),
and the fortify routines have been rearranged.

Update the Kconfig to reflect the reality of the current situation.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 security/Kconfig | 3 +++
 1 file changed, 3 insertions(+)

diff mbox series

Patch

diff --git a/security/Kconfig b/security/Kconfig
index 0ced7fd33e4d..fe6c0395fa02 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -191,6 +191,9 @@  config HARDENED_USERCOPY_PAGESPAN
 config FORTIFY_SOURCE
 	bool "Harden common str/mem functions against buffer overflows"
 	depends on ARCH_HAS_FORTIFY_SOURCE
+	# https://bugs.llvm.org/show_bug.cgi?id=50322
+	# https://bugs.llvm.org/show_bug.cgi?id=41459
+	depends on !CC_IS_CLANG
 	help
 	  Detect overflows of buffers in common string and memory functions
 	  where the compiler can determine and validate the buffer sizes.