From patchwork Mon Jul 10 12:14:35 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13306833 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 30414EB64D9 for ; Mon, 10 Jul 2023 12:14:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231307AbjGJMOu (ORCPT ); Mon, 10 Jul 2023 08:14:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56536 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229759AbjGJMOq (ORCPT ); Mon, 10 Jul 2023 08:14:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 41775180; Mon, 10 Jul 2023 05:14:41 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5D4BE60FD9; Mon, 10 Jul 2023 12:14:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EE57AC433C9; Mon, 10 Jul 2023 12:14:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1688991280; bh=keXlJlAzhceOANDhcIRA1uDchUR8isMCDIVgVQwTE4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DuJ8f0e72x8Q5m1yjEwl9Gx7RYAGn2V9Cy601y7bD2ecK4X4cHGOOCN0Kkzlnm/B3 /2Lmy9WhuBpa1bQKtGkK0dXCieP76n0BgarlhMvBqdMNAkvzz9J9zgm+ibjg0+Ijfj TqpJCkszJkzFxo61d7eKrA0eZwQ4vD9UJa01YO1hxM3kR8Eu3XYFuSULFdPGsDReS5 OGQR0/iMwLY42VlDMqFVIjNHPEr2o82sOyYLwkPmOFUpLH4S40fMyzcRN3tE/59W96 gfCtOUtvkpx4KaOLbaXFpx49s4zylVPvUdchhPIbP86VwaJKXQf7vyunHfkhtokiQG OfTRE9rzzx++A== From: "Masami Hiramatsu (Google)" To: Peter Zijlstra Cc: Petr Pavlu , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, samitolvanen@google.com, x86@kernel.org, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Masami Hiramatsu Subject: [RFC PATCH 2/2] x86/kprobes: Prohibit probing on compiler generated CFI checking code Date: Mon, 10 Jul 2023 21:14:35 +0900 Message-Id: <168899127520.80889.15418363018799407058.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <168899125356.80889.17967397360941194229.stgit@devnote2> References: <168899125356.80889.17967397360941194229.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Prohibit probing on the compiler generated CFI typeid checking code because it is used for decoding typeid when CFI error happens. The compiler generates the following instruction sequence for indirect call checks on x86;   movl -, %r10d ; 6 bytes addl -4(%reg), %r10d ; 4 bytes je .Ltmp1 ; 2 bytes ud2 ; <- regs->ip And handle_cfi_failure() decodes these instructions (movl and addl) for the typeid and the target address. Thus if we put a kprobe on those instructions, the decode will fail and report a wrong typeid and target address. Signed-off-by: Masami Hiramatsu (Google) Acked-by: Peter Zijlstra (Intel) --- arch/x86/kernel/kprobes/core.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index f7f6042eb7e6..fa8c2b41cbaf 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -54,6 +54,7 @@ #include #include #include +#include #include "common.h" @@ -293,7 +294,40 @@ static int can_probe(unsigned long paddr) #endif addr += insn.length; } + if (IS_ENABLED(CONFIG_CFI_CLANG)) { + /* + * The compiler generates the following instruction sequence + * for indirect call checks and cfi.c decodes this; + * + *  movl -, %r10d ; 6 bytes + * addl -4(%reg), %r10d ; 4 bytes + * je .Ltmp1 ; 2 bytes + * ud2 ; <- regs->ip + * .Ltmp1: + * + * Also, these movl and addl are used for showing expected + * type. So those must not be touched. + */ + __addr = recover_probed_instruction(buf, addr); + if (!__addr) + return 0; + + if (insn_decode_kernel(&insn, (void *)__addr) < 0) + return 0; + + if (insn.opcode.value == 0xBA) + offset = 12; + else if (insn.opcode.value == 0x3) + offset = 6; + else + goto out; + + /* This movl/addl is used for decoding CFI. */ + if (is_cfi_trap(addr + offset)) + return 0; + } +out: return (addr == paddr); }