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=-13.0 required=3.0 tests=BAYES_00,HK_RANDOM_FROM, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE 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 CD7E8C433E0 for ; Sun, 10 Jan 2021 16:02:50 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3971D22483 for ; Sun, 10 Jan 2021 16:02:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3971D22483 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=bu.edu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:36056 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kydB2-000549-SL for qemu-devel@archiver.kernel.org; Sun, 10 Jan 2021 11:02:48 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:52820) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kyd9x-0004Xo-76 for qemu-devel@nongnu.org; Sun, 10 Jan 2021 11:01:42 -0500 Received: from relay64.bu.edu ([128.197.228.104]:57478) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kyd9u-0008CZ-RF for qemu-devel@nongnu.org; Sun, 10 Jan 2021 11:01:40 -0500 X-Envelope-From: alxndr@bu.edu X-BU-AUTH: mozz.bu.edu [128.197.127.33] Received: from BU-AUTH (localhost.localdomain [127.0.0.1]) (authenticated bits=0) by relay64.bu.edu (8.14.3/8.14.3) with ESMTP id 10AG0eNM030223 (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 10 Jan 2021 11:00:43 -0500 Date: Sun, 10 Jan 2021 11:00:40 -0500 From: Alexander Bulekov To: Qiuhao Li Subject: Re: [PATCH v4 1/7] fuzz: accelerate non-crash detection Message-ID: <20210110160040.uqlohbzr3viqhyxy@mozz.bu.edu> References: <20210107041827.sztisz72urbhxflx@mozz.bu.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Received-SPF: pass client-ip=128.197.228.104; envelope-from=alxndr@bu.edu; helo=relay64.bu.edu X-Spam_score_int: -15 X-Spam_score: -1.6 X-Spam_bar: - X-Spam_report: (-1.6 / 5.0 requ) BAYES_00=-1.9, HK_RANDOM_ENVFROM=0.001, HK_RANDOM_FROM=0.999, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: thuth@redhat.com, qemu-devel@nongnu.org, darren.kenny@oracle.com, bsd@redhat.com, stefanha@redhat.com, pbonzini@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 210110 2110, Qiuhao Li wrote: > On Wed, 2021-01-06 at 23:18 -0500, Alexander Bulekov wrote: > > On 201229 1240, Qiuhao Li wrote: > > > We spend much time waiting for the timeout program during the > > > minimization > > > process until it passes a time limit. This patch hacks the CLOSED > > > (indicates > > > the redirection file closed) notification in QTest's output if it > > > doesn't > > > crash. > > > > > > Test with quadrupled trace input at: > > > https://bugs.launchpad.net/qemu/+bug/1890333/comments/1 > > > > > > Original version: > > > real 1m37.246s > > > user 0m13.069s > > > sys 0m8.399s > > > > > > Refined version: > > > real 0m45.904s > > > user 0m16.874s > > > sys 0m10.042s > > > > > > Signed-off-by: Qiuhao Li > > > --- > > > scripts/oss-fuzz/minimize_qtest_trace.py | 41 ++++++++++++++++-- > > > ------ > > > 1 file changed, 28 insertions(+), 13 deletions(-) > > > > > > diff --git a/scripts/oss-fuzz/minimize_qtest_trace.py > > > b/scripts/oss-fuzz/minimize_qtest_trace.py > > > index 5e405a0d5f..aa69c7963e 100755 > > > --- a/scripts/oss-fuzz/minimize_qtest_trace.py > > > +++ b/scripts/oss-fuzz/minimize_qtest_trace.py > > > @@ -29,30 +29,46 @@ whether the crash occred. Optionally, manually > > > set a string that idenitifes the > > > crash by setting CRASH_TOKEN= > > > """.format((sys.argv[0]))) > > > > > > +deduplication_note = """\n\ > > > +Note: While trimming the input, sometimes the mutated trace > > > triggers a different > > > +crash output but indicates the same bug. Under this situation, our > > > minimizer is > > > +incapable of recognizing and stopped from removing it. In the > > > future, we may > > > +use a more sophisticated crash case deduplication method. > > > +\n""" > > > + > > > def check_if_trace_crashes(trace, path): > > > - global CRASH_TOKEN > > > with open(path, "w") as tracefile: > > > tracefile.write("".join(trace)) > > > > > > - rc = subprocess.Popen("timeout -s 9 {timeout}s {qemu_path} > > > {qemu_args} 2>&1\ > > > + proc = subprocess.Popen("timeout {timeout}s {qemu_path} > > > {qemu_args} 2>&1\ > > > > Why remove the -s 9 here? I ran into a case where the minimizer got > > stuck on one iteration. Adding back "sigkill" to the timeout can be a > > safety net to catch those bad cases. > > -Alex > > Hi Alex, > > After reviewed this patch again, I think this get-stuck bug may be > caused by code: > > - return CRASH_TOKEN in output Hi, Thanks for fixing this. Strangely, I was able to fix it by swapping the b'' for a ' ' when I was stuck on a testcase a few days ago. vvv > + for line in iter(rc.stdout.readline, b''): > + if "CLOSED" in line: > + return False > + if CRASH_TOKEN in line: > + return True > I think your proposed change essentially does the same? -Alex > I assumed there are only two end cases in lines of stdout, but while we > are trimming the trace input, the crash output (second-to-last line) > may changes, in which case we will go through the output and fail to > find "CLOSED" and CRASH_TOKEN, thus get stuck in the loop above. > > To fix this bug and get a more trimmed input trace, we can: > > Use the first three words of the second-to-last line instead of the > whole string, which indicate the type of crash as the token. > > - CRASH_TOKEN = output.splitlines()[-2] > + CRASH_TOKEN = " ".join(outs.splitlines()[-2].split()[0:3]) > > If we reach the end of a subprocess' output, return False. > > + if line == "": > + return False > > I fix it in [PATCH v7 1/7] and give an example. Could you review again? > Thanks :-) > > FYI, I mentioned this situation firstly in [PATCH 1/4], where I gave a > more detailed example: > > https://lists.gnu.org/archive/html/qemu-devel/2020-12/msg05888.html > > > > > > < {trace_path}".format(timeout=TIMEOUT, > > > qemu_path=QEMU_PATH, > > > qemu_args=QEMU_ARGS, > > > trace_path=path), > > > shell=True, > > > stdin=subprocess.PIPE, > > > - stdout=subprocess.PIPE) > > > - stdo = rc.communicate()[0] > > > - output = stdo.decode('unicode_escape') > > > - if rc.returncode == 137: # Timed Out > > > - return False > > > - if len(output.splitlines()) < 2: > > > - return False > > > - > > > + stdout=subprocess.PIPE, > > > + encoding="utf-8") > > > + global CRASH_TOKEN > > > if CRASH_TOKEN is None: > > > - CRASH_TOKEN = output.splitlines()[-2] > > > + try: > > > + outs, _ = proc.communicate(timeout=5) > > > + CRASH_TOKEN = outs.splitlines()[-2] > > > + except subprocess.TimeoutExpired: > > > + print("subprocess.TimeoutExpired") > > > + return False > > > + print("Identifying Crashes by this string: > > > {}".format(CRASH_TOKEN)) > > > + global deduplication_note > > > + print(deduplication_note) > > > + return True > > > > > > - return CRASH_TOKEN in output > > > + for line in iter(proc.stdout.readline, b''): > > > + if "CLOSED" in line: > > > + return False > > > + if CRASH_TOKEN in line: > > > + return True > > > + > > > + return False > > > > > > > > > def minimize_trace(inpath, outpath): > > > @@ -66,7 +82,6 @@ def minimize_trace(inpath, outpath): > > > print("Crashed in {} seconds".format(end-start)) > > > TIMEOUT = (end-start)*5 > > > print("Setting the timeout for {} seconds".format(TIMEOUT)) > > > - print("Identifying Crashes by this string: > > > {}".format(CRASH_TOKEN)) > > > > > > i = 0 > > > newtrace = trace[:] > > > -- > > > 2.25.1 > > > >