From mboxrd@z Thu Jan 1 00:00:00 1970 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 E6676C54EE9 for ; Thu, 8 Sep 2022 15:01:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231622AbiIHPBi (ORCPT ); Thu, 8 Sep 2022 11:01:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53162 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232766AbiIHPBb (ORCPT ); Thu, 8 Sep 2022 11:01:31 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id F2474ED9B7; Thu, 8 Sep 2022 08:01:28 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C4CF561D38; Thu, 8 Sep 2022 15:01:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D03C4C433C1; Thu, 8 Sep 2022 15:01:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1662649287; bh=pCqMEF+hRGXhMV+bGw+tm59DrO7QZ5nD5ZCcllSjM/g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dY1apBZg3O93aJIBk19Yd3jF5YPM60PkzpYA8YGXIUnNpQJlj5a36B7Xdd77fqQdb MOy1Ol7wuY3KPZRUFAQuZEjznAilft0+6d3a3smt4kFWExvbpX0WjFGfhTvEFT0cHP tq9AfEcf/DgxaZq7ZE47yOTlkXq8bCLhpn0sFagS8cygr2uR7J7rPHUModY7FIoOmY zgIjtQt2PvzU8VPrCrilXnySvPtls+ul1/7Ff9dMCJDFKRvBBp6JfFNlCS7uOV6myb aIBfhcATkRf72jVv/BoUoIk12Xedsr8paI9IAh7kNFi0jg8lhKDXOHGFnia/iaSbE+ O7u4EU3GoecHw== From: "Masami Hiramatsu (Google)" To: Peter Zijlstra , Josh Poimboeuf Cc: Steven Rostedt , Masami Hiramatsu , Ingo Molnar , Suleiman Souhlal , bpf , linux-kernel@vger.kernel.org, Borislav Petkov , x86@kernel.org Subject: [PATCH v3 1/2] x86/kprobes: Fix kprobes instruction boudary check with CONFIG_RETHUNK Date: Fri, 9 Sep 2022 00:01:22 +0900 Message-Id: <166264928214.775585.6657611968575138295.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <166264927154.775585.16570756675363838701.stgit@devnote2> References: <166264927154.775585.16570756675363838701.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Masami Hiramatsu (Google) Since the CONFIG_RETHUNK and CONFIG_SLS will use INT3 for stopping speculative execution after RET instruction, kprobes always failes to check the probed instruction boundary by decoding the function body if the probed address is after such sequence. (Note that some conditional code blocks will be placed after function return, if compiler decides it is not on the hot path.) This is because kprobes expects kgdb puts the INT3 as a software breakpoint and it will replace the original instruction. But these INT3 are not such purpose, it doesn't need to recover the original instruction. To avoid this issue, kprobes checks whether the INT3 is owned by kgdb or not, and if so, stop decoding and make it fail. The other INT3 will come from CONFIG_RETHUNK/CONFIG_SLS and those can be treated as a one-byte instruction. Signed-off-by: Masami Hiramatsu (Google) Suggested-by: Peter Zijlstra Fixes: e463a09af2f0 ("x86: Add straight-line-speculation mitigation") Cc: stable@vger.kernel.org --- arch/x86/kernel/kprobes/core.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 4c3c27b6aea3..c6dd7ae68c8f 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include #include @@ -283,12 +284,15 @@ static int can_probe(unsigned long paddr) if (ret < 0) return 0; +#ifdef CONFIG_KGDB /* - * Another debugging subsystem might insert this breakpoint. - * In that case, we can't recover it. + * If there is a dynamically installed kgdb sw breakpoint, + * this function should not be probed. */ - if (insn.opcode.bytes[0] == INT3_INSN_OPCODE) + if (insn.opcode.bytes[0] == INT3_INSN_OPCODE && + kgdb_has_hit_break(addr)) return 0; +#endif addr += insn.length; }