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 X-Spam-Level: X-Spam-Status: No, score=-10.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham 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 0991EC433F4 for ; Mon, 27 Aug 2018 18:58:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BD998208DA for ; Mon, 27 Aug 2018 18:58:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="QYmc8T2y" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BD998208DA Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727756AbeH0Wpu (ORCPT ); Mon, 27 Aug 2018 18:45:50 -0400 Received: from mail-pf1-f202.google.com ([209.85.210.202]:38099 "EHLO mail-pf1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727401AbeH0Wpt (ORCPT ); Mon, 27 Aug 2018 18:45:49 -0400 Received: by mail-pf1-f202.google.com with SMTP id e15-v6so15488pfi.5 for ; Mon, 27 Aug 2018 11:57:59 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=eqpJL+HTAUaly6TthXYPjkvNkyzv1PO/fAC6zdW/LP4=; b=QYmc8T2yUkQH5+tuKTLSQ5xRntLwae+jQotcuh9fniFtflY9ybVDubyF7tv/UFzzit jP5HzN2cyW5jpYOkeyNjZK2KIKQZLvX3ZcgacdgFjElEW5xQVlaSQ7RT4Bao2Zjh0hrn ms0HIGB0KPnZe2YhnNjcL5ebt/UWgZXiD+b9k0r1BPr4Hgtx85YuJhHuCSUYj1nawKlM VpbPyfj6tXqDfW5TYB84o+1NuXHvCuAjUMBcvmokHZyX0EJb2uC0ZFdKbBqk27/G4xpz QV4NYGeaCyC3RE03SSrlT84RpeIEcRbLqUASg7BPoVJ2b3vJCEU6CDqGdRzuGCAzJHLZ uEHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=eqpJL+HTAUaly6TthXYPjkvNkyzv1PO/fAC6zdW/LP4=; b=EWdmSk7ZoSYTLi5DV4d1EfyioZpfWEttTVjMNjAgsKsBb0plUBcIp+BDVNjfYQ9+71 +47XM3sjZOkqU2zA2gJ/Y7j2TICzCr/Rmt4wlUd69wIZQzBpevIgiEQSRBX3o3oP+L/O YBtETfdcu151PGD1a/L3pZqSsmH0Y+jt/Rd1Ik/46NE40CvgIPkTzm+li4IL5caF31Aw DWFs5tqlxBsQyUH18E2kZlIAO+TdjOS1x7tONs/N8CXwHhRTF/FznoORMD8/Amx3N2uc nPHdOTrnp27diqL7yvckBW1yt/2RaLfsFsNsgk2lXJCfezVmdX5vfUOuVaWqzuF08YGm 7DnA== X-Gm-Message-State: APzg51DDqI7UqEMFrNRISMfQ0v18YWz+ncSLcCS9j2Lbf3zmk42GeCYt IG7kdJ86r6zOnepdAH2crmAFo+jFJA== X-Google-Smtp-Source: ANB0VdZ2/PwcEwXqcNrjOb3NgeqNHewW6uRfXlDAuW1Yz16d4zCG1H6YpaY0gP9ZOY0qGsHkkGsqAOOnTw== X-Received: by 2002:a63:4541:: with SMTP id u1-v6mr5333pgk.104.1535396279373; Mon, 27 Aug 2018 11:57:59 -0700 (PDT) Date: Mon, 27 Aug 2018 20:56:27 +0200 In-Reply-To: <20180827185631.163506-1-jannh@google.com> Message-Id: <20180827185631.163506-4-jannh@google.com> Mime-Version: 1.0 References: <20180827185631.163506-1-jannh@google.com> X-Mailer: git-send-email 2.19.0.rc0.228.g281dcd1b4d0-goog Subject: [PATCH v2 3/7] x86: stop calling fixup_exception() from kprobe_fault_handler() From: Jann Horn To: Kees Cook , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Andy Lutomirski , kernel-hardening@lists.openwall.com, Tony Luck , Borislav Petkov , jannh@google.com Cc: linux-kernel@vger.kernel.org, dvyukov@google.com, linux-edac@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This removes the call into exception fixup that was added in commit c28f896634f2 ("[PATCH] kprobes: fix broken fault handling for x86_64"). On X86, kprobe_fault_handler() is called from two places: do_general_protection() (for #GP) and kprobes_fault() (for #PF). In both paths, the fixup_exception() call in the kprobe fault handler is redundant. For #GP, fixup_exception() is called immediately before kprobe_fault_handler() is invoked - if someone wanted to fix up our #GP, they've already done so, no need to try again. (This assumes that the kprobe's fault handler isn't going to do something crazy like changing RIP so that it suddenly points to an instruction that does userspace access.) For #PF on a kernel address from kernel space, after the kprobe fault handler has run, we'll go into no_context(), which calls fixup_exception(). Signed-off-by: Jann Horn --- arch/x86/kernel/kprobes/core.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 467ac22691b0..7315ac202aad 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1021,13 +1021,6 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) if (cur->fault_handler && cur->fault_handler(cur, regs, trapnr)) return 1; - /* - * In case the user-specified fault handler returned - * zero, try to fix up. - */ - if (fixup_exception(regs, trapnr)) - return 1; - /* fixup routine could not handle it. */ } -- 2.19.0.rc0.228.g281dcd1b4d0-goog