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[209.85.167.54]) by smtp.gmail.com with ESMTPSA id a30-20020a056512021e00b004fbacc3d0ecsm1954088lfo.249.2023.07.04.07.12.41 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jul 2023 07:12:41 -0700 (PDT) Received: by mail-lf1-f54.google.com with SMTP id 2adb3069b0e04-4fb7769f15aso8982256e87.0 for ; Tue, 04 Jul 2023 07:12:41 -0700 (PDT) X-Received: by 2002:a05:6512:2386:b0:4fb:763c:af54 with SMTP id c6-20020a056512238600b004fb763caf54mr11708321lfv.62.1688479961179; Tue, 04 Jul 2023 07:12:41 -0700 (PDT) MIME-Version: 1.0 References: <202307041023.bcdbbfc0-oliver.sang@intel.com> In-Reply-To: <202307041023.bcdbbfc0-oliver.sang@intel.com> From: Linus Torvalds Date: Tue, 4 Jul 2023 07:12:23 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [linus:master] [gup] a425ac5365: WARNING:at_mm/gup.c:#__get_user_pages To: kernel test robot Cc: oe-lkp@lists.linux.dev, lkp@intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Type: multipart/mixed; boundary="0000000000004cc04805ffa9e054" X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: EA9ADC002A X-Stat-Signature: ffcc4wxgwj48n8hac1r4pxez9z74nqdq X-HE-Tag: 1688479964-503082 X-HE-Meta: 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 oInynT/0 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --0000000000004cc04805ffa9e054 Content-Type: text/plain; charset="UTF-8" On Tue, 4 Jul 2023 at 00:03, kernel test robot wrote: > > we noticed this commit 'add a (temporary) warning' for the case that > 'anybody actually does anything quite this strange'. > and in our this test, the warning hits. just FYI. Yeah, so it looks like this is trinity doing system calls with random arguments, and that will obviously hit the whole "GUP will no longer expand the stack, warn if somebody seems to want to do GUP under the stack" test. So then it will warn if somebody passes in bogus addresses that *used* to maybe work. But with a random argument tester like trinity, passing in random bogus addresses is obviously expected, so the warning will trigger even if it's not something that we would not want to keep working. I do not have a good idea for how to not warn for things like syzbot and trinity that do random system calls, and only warn for any potential real applications that do crazy things and expect them to work. And I *do* want the backtrace from the warning (in this case, it shows that it's the "process_vm_readv/writev()" path, which actually might be worth adding stack expansion to, the same way __access_remote_vm() does). I guess I can do the limiting manually, and just avoid WARN_ON_ONCE(). If I do just "dump_stack()", will the kernel test robot react to that too? IOW, would a patch like the attached make the kernel test robot not react? 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