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=-10.5 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 90264C433F5 for ; Tue, 28 Aug 2018 20:14:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 49CE52087E for ; Tue, 28 Aug 2018 20:14:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="k9MstZk0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 49CE52087E 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 S1727389AbeH2AIE (ORCPT ); Tue, 28 Aug 2018 20:08:04 -0400 Received: from mail-pg1-f201.google.com ([209.85.215.201]:39291 "EHLO mail-pg1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727328AbeH2AID (ORCPT ); Tue, 28 Aug 2018 20:08:03 -0400 Received: by mail-pg1-f201.google.com with SMTP id q12-v6so1771130pgp.6 for ; Tue, 28 Aug 2018 13:14:48 -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=03TAXzBIbK9qSPjls82pb6bVgK3cZq6BxaYmPeOzPNA=; b=k9MstZk0c2zdNTFSvMTX0jVj6F0t2QStibNqEXye6Ey7CN7GTPilMG/QNGEft9wwy7 7z3CUVCrnrHtFjQjnkrsiBgHyXu+V4ix9rOiV4ZhUDLlcDEls7cQ49zmOUuIeITJ89J+ BBYyvErOgZn9brmOZMbBKpii+A8kEqmhE6h7D25Hru6B1N7gwxHGU+60IbF6vnTz/DUF 8eJg1VRws24//e00HOVbKSAPVB5SIPxY1rTRctGFQWg7LZDxNcVr9KHesDp/YyZOqnVd S4e9L3Tt7fufL0H57G4qQL0Kd9YsY1Wb0/g0gCfLQ0RoCOiCmnpeQbkLBeXym0aCP8mS ZUew== 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=03TAXzBIbK9qSPjls82pb6bVgK3cZq6BxaYmPeOzPNA=; b=SV2osJ0oLXVBEBXlsirlGtWnG/gSju7E8GRaHdRpPVYMe5Vt1CqjXJnClLfY1NGyOv g6m7IU9jtMJLlF9UvFXd13UxwSlqcBhz/7UYUG1p6ASSaMylUtqbEmNoj2/t9JfJsN5c Hg2xw9Pzhr4ueKiwHqH6cd7macfKi2XwSkfSlH121xmSDAw32ZQzI6RVYk8EPecu47W1 7wFIwTez9ofCW8N12dRJzQYbV6bqq0cBe6m9A9GspIX9GvSG5PijiFAz/+iVLX4CbEHj os8pGUaFfCJywNaH3rh1FlIrUDySeR3EqPxhL0mXsn4nXNFJcEN65zMBVGV9bNLmfKFL Vckw== X-Gm-Message-State: APzg51Ae6RkqLtR11GBl0rQxTwexKEuEwQGOe6p7w/VIjpq3G9Xc2iF2 KGfC+0B0aJfzsW9wlJSIifCApo7geA== X-Google-Smtp-Source: ANB0VdYgWZ5VfYWaGnKLfkPsMkmQJLzGAuQC5FQ4qD+JPJXy209W/KyIRBpY8ob3Rf+BctOyZwDckr/9yw== X-Received: by 2002:a63:4406:: with SMTP id r6-v6mr853725pga.64.1535487288321; Tue, 28 Aug 2018 13:14:48 -0700 (PDT) Date: Tue, 28 Aug 2018 22:14:17 +0200 In-Reply-To: <20180828201421.157735-1-jannh@google.com> Message-Id: <20180828201421.157735-4-jannh@google.com> Mime-Version: 1.0 References: <20180828201421.157735-1-jannh@google.com> X-Mailer: git-send-email 2.19.0.rc0.228.g281dcd1b4d0-goog Subject: [PATCH v3 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, jannh@google.com Cc: linux-kernel@vger.kernel.org, dvyukov@google.com, Masami Hiramatsu , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Alexander Viro , linux-fsdevel@vger.kernel.org, Borislav Petkov 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(). Acked-by: Masami Hiramatsu 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