From patchwork Mon Mar 15 18:02:28 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kees Cook X-Patchwork-Id: 12140327 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 95001C433DB for ; Mon, 15 Mar 2021 18:03:57 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id A8C9764F07 for ; Mon, 15 Mar 2021 18:03:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A8C9764F07 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-20940-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 11597 invoked by uid 550); 15 Mar 2021 18:02:54 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 11467 invoked from network); 15 Mar 2021 18:02:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=yYr9wVtQr+Yv2YCxxAWFJhlutYOKWxR3zpP8Meqzwc0=; b=PJ3T01c5ZmSw41q5MAxkemIUNEX541whNOtK/oVGkgDvEXke5s57A/1q9tzDzo+AEJ 17TwxsQhxMpKr12YLaf51slHhYzShk72wq3LA7Tf1jp2ZGhrKU21lUBPzS/02MQjUN4a 8BNS0yFQ9mNrfIeZXkahph53aQpbFJsZAfitI= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=yYr9wVtQr+Yv2YCxxAWFJhlutYOKWxR3zpP8Meqzwc0=; b=EYzSkLmNeNe5f+iEEVjocn52dJXFRCzaLGnaSldohXOuGKaThb8FcqaiUgqlioBVR9 k+94HiOPTDQ3LkBCpTKyD2k0RgKYF6tu2Z3P8MqLYhQqzvLahyeRCk4wib6fsF0tABW9 eSNnxe40XD/WMWOw2UeenXFP1bnOMgrpU1/xOJOQ/vLVQifTQYxfF2IQkmDujUwXOsa9 TKnCmWV/JMA75OHtmAtLunCZerNOobXQq4jydT7uSMRuktYv7EdH2jSri11EMwY9qUKG 94p5qrkX0YPrPtmuZZe24Exkt8F7V3HkHxqfXoLcohh5tvGbb1UPQuETm9Z5mdUr6ZvJ 83QQ== X-Gm-Message-State: AOAM530+bH2cx9FC9JQw0xX/su3YI5YXCaRBeq4vbE0q2pE64QeGLyfV yUkhw5rrWVt59oD2yeYpFWRK6A== X-Google-Smtp-Source: ABdhPJypLz3rt4xSDEfwAQI69keGjt8wki/cYUqoCZg01pG+rs+SU3iIC2Rhxqq4jRLey7oHOmrHHw== X-Received: by 2002:a65:6208:: with SMTP id d8mr260022pgv.365.1615831359582; Mon, 15 Mar 2021 11:02:39 -0700 (PDT) From: Kees Cook To: Thomas Gleixner Cc: Kees Cook , Elena Reshetova , x86@kernel.org, Andy Lutomirski , Peter Zijlstra , Catalin Marinas , Will Deacon , Mark Rutland , Alexander Potapenko , Alexander Popov , Ard Biesheuvel , Jann Horn , Vlastimil Babka , David Hildenbrand , Mike Rapoport , Andrew Morton , Jonathan Corbet , Randy Dunlap , kernel-hardening@lists.openwall.com, linux-hardening@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 5/6] arm64: entry: Enable random_kstack_offset support Date: Mon, 15 Mar 2021 11:02:28 -0700 Message-Id: <20210315180229.1224655-6-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210315180229.1224655-1-keescook@chromium.org> References: <20210315180229.1224655-1-keescook@chromium.org> MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; g=ab928f13a74b1e09ed2d4740c77a8520d58ab562; i=6FjHrMJQ1a03WxuPiMt8aIK5MW/T0bayLG0SuUm7Wt4=; m=DW/OKOjAEidoxl6ODEV6zN0c7U/uCvK1t/uZsIkKPaM=; p=MOQyOeWlIC4XP1YdIGtrtyC9k7Ng+ZO0cCzQ0e3ME/8= X-Patch-Sig: m=pgp; i=keescook@chromium.org; s=0x0x8972F4DFDC6DC026; b=iQIzBAABCgAdFiEEpcP2jyKd1g9yPm4TiXL039xtwCYFAmBPoTQACgkQiXL039xtwCZ8+hAAok1 EQH02pRdoiRp9m8tbYTx8Kv8urKXluNaNLKQ8VjvRmjYSBNnvpTWI/n09jSnhzsXmY3lP9KFBiiSR vTF18ZmisLjVh1++NAWmL4zJNQExvXHxdxXvrzs6I0wIm+3ULPb+9DxBwwzeFIOlTC0AHfkarOIvI JPzaUMXvv+p+TiFW12lULVfRIkjZeTY8diwqSzXhh0Z+sJFZt0H5C9CzgjNlKMnNDGj2r4ie5i14O 4pSTw5xa/wRNzIDemET+Cl6r5cxlzMmyUnwKxL8cQl2HF2ysqiZFcCqUrsFdHWMiO8p9js8+hJjdr DnVs/0zGx9OvIObQq8Cs6RXEWpOQT91MbY6iWdLYoP1I+4vwxcR7P2bIm8kvDtL/P+YEVghQCMAi/ Nbw7LFXshsWv4OkJT8XZvnuYTdN/6HIL6Pz1V74YC5b4+90rxYBfG6Di9MIxsJk6X3QQh6+yznoDJ YmtysrTNSPGMXjKDJfs3f3yKIpWSePYSb9w6LZMFUww5o0vdipqLGAv4onWHWsatjKjTN7Qi8Qy2v z/gu45senClYLMA4IqByUxpO7K0pVhkjIJ9bCuGqylQg37zdDD/h9fh1xGKCCzDeGBHjt88zBIQy0 1RmtN5iz/6GO6LViI+zmCV5RpDsDtBtZA7ZIuS5jlamNSIEmDoQBVdxK0QuCHdbw= Allow for a randomized stack offset on a per-syscall basis, with roughly 5 bits of entropy. (And include AAPCS rationale AAPCS thanks to Mark Rutland.) In order to avoid unconditional stack canaries on syscall entry (due to the use of alloca()), also disable stack protector to avoid triggering needless checks and slowing down the entry path. As there is no general way to control stack protector coverage with a function attribute[1], this must be disabled at the compilation unit level. This isn't a problem here, though, since stack protector was not triggered before: examining the resulting syscall.o, there are no changes in canary coverage (none before, none now). [1] a working __attribute__((no_stack_protector)) has been added to GCC and Clang but has not been released in any version yet: https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=346b302d09c1e6db56d9fe69048acb32fbb97845 https://reviews.llvm.org/rG4fbf84c1732fca596ad1d6e96015e19760eb8a9b Signed-off-by: Kees Cook --- arch/arm64/Kconfig | 1 + arch/arm64/kernel/Makefile | 5 +++++ arch/arm64/kernel/syscall.c | 10 ++++++++++ 3 files changed, 16 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 1f212b47a48a..2d0e5f544429 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -146,6 +146,7 @@ config ARM64 select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_PFN_VALID select HAVE_ARCH_PREL32_RELOCATIONS + select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_STACKLEAK select HAVE_ARCH_THREAD_STRUCT_WHITELIST diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile index ed65576ce710..6cc97730790e 100644 --- a/arch/arm64/kernel/Makefile +++ b/arch/arm64/kernel/Makefile @@ -9,6 +9,11 @@ CFLAGS_REMOVE_ftrace.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_insn.o = $(CC_FLAGS_FTRACE) CFLAGS_REMOVE_return_address.o = $(CC_FLAGS_FTRACE) +# Remove stack protector to avoid triggering unneeded stack canary +# checks due to randomize_kstack_offset. +CFLAGS_REMOVE_syscall.o = -fstack-protector -fstack-protector-strong +CFLAGS_syscall.o += -fno-stack-protector + # Object file lists. obj-y := debug-monitors.o entry.o irq.o fpsimd.o \ entry-common.o entry-fpsimd.o process.o ptrace.o \ diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index b9cf12b271d7..58227a1c207e 100644 --- a/arch/arm64/kernel/syscall.c +++ b/arch/arm64/kernel/syscall.c @@ -5,6 +5,7 @@ #include #include #include +#include #include #include @@ -43,6 +44,8 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno, { long ret; + add_random_kstack_offset(); + if (scno < sc_nr) { syscall_fn_t syscall_fn; syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)]; @@ -55,6 +58,13 @@ static void invoke_syscall(struct pt_regs *regs, unsigned int scno, ret = lower_32_bits(ret); regs->regs[0] = ret; + + /* + * The AAPCS mandates a 16-byte (i.e. 4-bit) aligned SP at + * function boundaries. We want at least 5 bits of entropy so we + * must randomize at least SP[8:4]. + */ + choose_random_kstack_offset(get_random_int() & 0x1FF); } static inline bool has_syscall_work(unsigned long flags)