From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0052F381D8; Fri, 24 Nov 2023 18:04:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Zv1e0BNL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BB55C433C8; Fri, 24 Nov 2023 18:04:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700849041; bh=nszA1F05m/lC/J8PTzfim4spp5Jqv9Aec6nVf6wQQYM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Zv1e0BNLofL7QZCP68tMTGjqVhs9uXkrOC5/Zb9UywTO0OfJG9fp6nhqckfGrKV7x fFaVh8WgGYPtcDaWqA5WJG5E9Wbw6MWzn9wkcHJQAHurItOK3B7KFKHVCPf8wyxhER rISEpIz0ku0wHEx1AYjOUl8/AIyZaH7hG3TLbATY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Nathan Chancellor , Josh Poimboeuf , "Borislav Petkov (AMD)" , Nick Desaulniers , Marco Elver , Sasha Levin Subject: [PATCH 6.6 004/530] x86/retpoline: Make sure there are no unconverted return thunks due to KCSAN Date: Fri, 24 Nov 2023 17:42:50 +0000 Message-ID: <20231124172028.240757893@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124172028.107505484@linuxfoundation.org> References: <20231124172028.107505484@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josh Poimboeuf [ Upstream commit 2d7ce49f58dc95495b3e22e45d2be7de909b2c63 ] Enabling CONFIG_KCSAN leads to unconverted, default return thunks to remain after patching. As David Kaplan describes in his debugging of the issue, it is caused by a couple of KCSAN-generated constructors which aren't processed by objtool: "When KCSAN is enabled, GCC generates lots of constructor functions named _sub_I_00099_0 which call __tsan_init and then return. The returns in these are generally annotated normally by objtool and fixed up at runtime. But objtool runs on vmlinux.o and vmlinux.o does not include a couple of object files that are in vmlinux, like init/version-timestamp.o and .vmlinux.export.o, both of which contain _sub_I_00099_0 functions. As a result, the returns in these functions are not annotated, and the panic occurs when we call one of them in do_ctors and it uses the default return thunk. This difference can be seen by counting the number of these functions in the object files: $ objdump -d vmlinux.o|grep -c "<_sub_I_00099_0>:" 2601 $ objdump -d vmlinux|grep -c "<_sub_I_00099_0>:" 2603 If these functions are only run during kernel boot, there is no speculation concern." Fix it by disabling KCSAN on version-timestamp.o and .vmlinux.export.o so the extra functions don't get generated. KASAN and GCOV are already disabled for those files. [ bp: Massage commit message. ] Closes: https://lore.kernel.org/lkml/20231016214810.GA3942238@dev-arch.thelio-3990X/ Reported-by: Nathan Chancellor Signed-off-by: Josh Poimboeuf Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Nick Desaulniers Acked-by: Marco Elver Tested-by: Nathan Chancellor Link: https://lore.kernel.org/r/20231017165946.v4i2d4exyqwqq3bx@treble Signed-off-by: Sasha Levin --- init/Makefile | 1 + scripts/Makefile.vmlinux | 1 + 2 files changed, 2 insertions(+) diff --git a/init/Makefile b/init/Makefile index ec557ada3c12e..cbac576c57d63 100644 --- a/init/Makefile +++ b/init/Makefile @@ -60,4 +60,5 @@ include/generated/utsversion.h: FORCE $(obj)/version-timestamp.o: include/generated/utsversion.h CFLAGS_version-timestamp.o := -include include/generated/utsversion.h KASAN_SANITIZE_version-timestamp.o := n +KCSAN_SANITIZE_version-timestamp.o := n GCOV_PROFILE_version-timestamp.o := n diff --git a/scripts/Makefile.vmlinux b/scripts/Makefile.vmlinux index 3cd6ca15f390d..c9f3e03124d7f 100644 --- a/scripts/Makefile.vmlinux +++ b/scripts/Makefile.vmlinux @@ -19,6 +19,7 @@ quiet_cmd_cc_o_c = CC $@ ifdef CONFIG_MODULES KASAN_SANITIZE_.vmlinux.export.o := n +KCSAN_SANITIZE_.vmlinux.export.o := n GCOV_PROFILE_.vmlinux.export.o := n targets += .vmlinux.export.o vmlinux: .vmlinux.export.o -- 2.42.0