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[209.85.220.65]) by mx.google.com with SMTPS id f9sor8017338lfl.55.2019.04.30.06.24.05 for (Google Transport Security); Tue, 30 Apr 2019 06:24:06 -0700 (PDT) Received-SPF: pass (google.com: domain of gorcunov@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=PxutZQVn; spf=pass (google.com: domain of gorcunov@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=gorcunov@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:content-transfer-encoding:in-reply-to :user-agent; bh=qnpMUYkMmL9pa1NwW2JEoP1ItjcZEv+YmAjkVOUYqyQ=; b=PxutZQVnmGiTrO83tBry4NYVOaB4lJN09Oxip41bc355LYSr1LYeo1lMf41kY1dbPT Az2YTmBmBe5x538dT+JRe1+JYJCz1FoZpsDQi9caft0FfB24tBWxwTJv5idXE3tCj309 ndFGbbBo2539UPe3H3O748UbjUEB5fXovu/9xWmEfhXYjNsDa8MGUA7FNgzTEwcV2NYx BzUCxvrUpvXfcEOn53rFrUqaBy+pwlNLr7oHR8TPl+xrEZ1Otp/fmWcn5hIPL8+9gurK qq05lb0/OOuJZi6nG1tjGqZ27/O0Si7Z+rZrnHkVNiZ1eEaLz2uJksbogv7Sccdikqvu +sog== X-Google-Smtp-Source: APXvYqxY66JUV3S/EHKt8chK3vxOG3tpmuDiZ0EEFbAfPD2vCxwBJVAqoqvpolQPE+tgSK7CerPsJg== X-Received: by 2002:a19:5507:: with SMTP id n7mr15109749lfe.140.1556630645642; Tue, 30 Apr 2019 06:24:05 -0700 (PDT) Received: from uranus.localdomain ([5.18.103.226]) by smtp.gmail.com with ESMTPSA id s24sm7499626ljs.30.2019.04.30.06.24.03 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 30 Apr 2019 06:24:04 -0700 (PDT) Received: by uranus.localdomain (Postfix, from userid 1000) id 7333A46019C; Tue, 30 Apr 2019 16:24:03 +0300 (MSK) Date: Tue, 30 Apr 2019 16:24:03 +0300 From: Cyrill Gorcunov To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: Kirill Tkhai , brgl@bgdev.pl, arunks@codeaurora.org, geert+renesas@glider.be, mhocko@kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, ldufour@linux.ibm.com, rppt@linux.ibm.com, mguzik@redhat.com, mkoutny@suse.cz, vbabka@suse.cz, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap_sem Message-ID: <20190430132403.GG2673@uranus.lan> References: <20190418182321.GJ3040@uranus.lan> <20190430081844.22597-1-mkoutny@suse.com> <20190430081844.22597-2-mkoutny@suse.com> <4c79fb09-c310-4426-68f7-8b268100359a@virtuozzo.com> <20190430093808.GD2673@uranus.lan> <1a7265fa-610b-1f2a-e55f-b3a307a39bf2@virtuozzo.com> <20190430104517.GF2673@uranus.lan> <20190430105609.GA23779@blackbody.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190430105609.GA23779@blackbody.suse.cz> User-Agent: Mutt/1.11.3 (2019-02-01) 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: On Tue, Apr 30, 2019 at 12:56:10PM +0200, Michal Koutný wrote: > On Tue, Apr 30, 2019 at 01:45:17PM +0300, Cyrill Gorcunov wrote: > > It setups these parameters unconditionally. I need to revisit > > this moment. Technically (if only I'm not missing something > > obvious) we might have a race here with prctl setting up new > > params, but this should be harmless since most of them (except > > stack setup) are purely informative data. > > FTR, when I reviewed that usage, I noticed it was missing the > synchronization. My understanding was that the mm_struct isn't yet > shared at this moment. I can see some of the operations take place after > flush_old_exec (where current->mm = mm_struct), so potentially it is > shared since then. OTOH, I guess there aren't concurrent parties that > could access the field at this stage of exec. Just revisited this code -- we're either executing prctl, either execve. Since both operates with current task we're safe.