Received: by 2002:a05:6a10:a0d1:0:0:0:0 with SMTP id j17csp308099pxa; Wed, 12 Aug 2020 02:31:49 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyL0MycKGOTa+VdstoXBmT+zigmAOxa0b3bRoiIbX8yRvDpPopMHFjedoiMRyoS/tZDDJqB X-Received: by 2002:a17:906:4ec6:: with SMTP id i6mr30227973ejv.358.1597224708992; Wed, 12 Aug 2020 02:31:48 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1597224708; cv=none; d=google.com; s=arc-20160816; b=tOKvM37esIytfw80BR+p4kfujTmpNNk7CkP5VRI9sHxTZKMe1buEwMkRmlLCb+PCyN /E5D2N7hTMR5h5C4npNepTTnTV25HRsKe8MFa4yM+zlHCmDaAHHTXU4ubRnXx6VJ18Ll CWwB81NG2WoyAURXSNHrjS0/M55mMlzdr7Y8QCX4CD6SRILljPSsVbHfK3YbZ/iWjU38 lxGNpjNVttzSj589I8EGVA99gWy0XhGXzgVIy61quRG0QqLwqcVoDFwyPPYYbeK/OCq+ 6UoHktJbPJk3IPDpOFRIK7Y9TNsM/20x0B9wbeN87kilv24dAAPySEqkuxiHcFBKvpHW AGsQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:in-reply-to:content-disposition :mime-version:references:message-id:subject:cc:to:from:date; bh=/spDadV99v25gTijXwgQHGrCLS4nqU1baWLsxWhRFRE=; b=jMip8n2n13FYoTg/6f8scWBQ2RzJNp1r+wOSQWAUuwqVcKgQjAAoxC1BTZ2nAPzhOK Q1VH4VULFuH4Z7FODCjq1AozpdM95i8QK4oo8BPpomCZKymgoVE/T+FhM1ieQBmfAx0N RwflVDoUJkjpCxfY2I82cs0s0eet3tqRRQ9jZM3zlAiYKPMD25Iga9PQHZinUnnxI1ZY /qTyN5iIubdx59JN17rdtY8YknSp1leg5unND4YTsZazCaR+WRsuLBHPgJsjmsJYOZ0+ Cm9xZfjKSnR1XOy+22agwwFOc1MSEor301/Tk1tj5fVHlkyfNo9ldi5HT6Q9vg6K9kQZ PrKw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id t19si772733ejd.62.2020.08.12.02.31.26; Wed, 12 Aug 2020 02:31:48 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726712AbgHLJaz (ORCPT + 99 others); Wed, 12 Aug 2020 05:30:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:33812 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726595AbgHLJaz (ORCPT ); Wed, 12 Aug 2020 05:30:55 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 99660AEAC; Wed, 12 Aug 2020 09:31:15 +0000 (UTC) Date: Wed, 12 Aug 2020 11:31:14 +0200 From: Cyril Hrubis To: Andy Lutomirski Cc: Peter Zijlstra , Alexandre Chartre , kernel test robot , LKML , lkp@lists.01.org, Thomas Gleixner , ltp@lists.linux.it Subject: Re: [LTP] [x86/entry] 2bbc68f837: ltp.ptrace08.fail Message-ID: <20200812093114.GA13676@yuki.lan> References: <87y2onbdtb.fsf@nanos.tec.linutronix.de> <8E41B15F-D567-4C52-94E9-367015480345@amacapital.net> <20200616132705.GW2531@hirez.programming.kicks-ass.net> <20200617131742.GD8389@yuki.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi! > do_debug is a bit of a red herring here. ptrace should not be able to > put a breakpoint on a kernel address, period. I would just pick a > fixed address that's in the kernel text range or even just in the > pre-KASLR text range and make sure it gets rejected. Maybe try a few > different addresses for good measure. I've looked at the code and it seems like this would be a bit more complicated since the breakpoint is set by an accident in a race and the call still fails. Which is why the test triggers the breakpoint and causes infinite loop in the kernel... I guess that we could instead read back the address with PTRACE_PEEKUSER, so something as: break_addr = ptrace(PTRACE_PEEKUSER, child_pid, (void *)offsetof(struct user, u_debugreg[0]), NULL); if (break_addr == kernel_addr) tst_res(TFAIL, "ptrace() set break on a kernel address"); -- Cyril Hrubis chrubis@suse.cz