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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E5E0C433EF for ; Tue, 5 Jul 2022 15:43:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9337C6B0071; Tue, 5 Jul 2022 11:42:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8E3466B0073; Tue, 5 Jul 2022 11:42:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7AC026B0074; Tue, 5 Jul 2022 11:42:59 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 692F26B0071 for ; Tue, 5 Jul 2022 11:42:59 -0400 (EDT) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 28FC06093C for ; Tue, 5 Jul 2022 15:42:59 +0000 (UTC) X-FDA: 79653464478.01.18124F1 Received: from mail-yb1-f177.google.com (mail-yb1-f177.google.com [209.85.219.177]) by imf19.hostedemail.com (Postfix) with ESMTP id BCB6C1A0058 for ; Tue, 5 Jul 2022 15:42:58 +0000 (UTC) Received: by mail-yb1-f177.google.com with SMTP id 64so13229427ybt.12 for ; Tue, 05 Jul 2022 08:42:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=kUzw94hBwwicZTDoD8iw9qTQlYL+xAA3YQavMnnyh1w=; b=AdcOA4QW2Wt+aFRE/Osn5xOa+MNHAKfkNyzyPxkICiLjpU9bC1Ch5pGQcjRiFcmSwf cXPsCL/4kYVrt6xMAWwlTuRE2425XdvSJBS+NDRf5TVTK9IMWOwKMaYvLFU6zI5LrN78 /Bz/XqsCDZSa5klnv3S1fsMIuLQ09cWtt8G125L/vkRD49CytleRK1kfzEkpLQoJEpum GaUsVbq4DAEFC/LiygZQUgqxK4+CXib0RNbrelev3p6lfgfEsRUn5ndALcU0RbroKb7H TFpA1AFf96ihtdPKx7kl0iTfBCZMSG0YTMHtoU3bhh0XZzWz2HVYWFg4Vu8z1eHdMLf9 yXrA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=kUzw94hBwwicZTDoD8iw9qTQlYL+xAA3YQavMnnyh1w=; b=vW506pcihfX93fe7Yjo5AX1MznhRhC1rPXzCS+NLOn1X+JTIqJcvYduWOBvj1VJjAN eooHOLcXTQ/ZKbSZeb40VpIisZPQFjln/gC1gGYs2UTcrssxwgCSunrIpQ/8BcHrQX3c UpoKTfttcn+rKKomZd6WpixAn50SiNy9pHAILLa02cqbEBfJJIcxoMKgwFo+1IRUIRpm COkZHzADExdkkDEGzyaieG/vL8QmJHtKKDsJ/J8CR/g6cL4+2hGvYw7WIHNsittrYdXT jXuj8mnXX0VpbI3EzWNkZGNG416TAHZG8tNNVs6OQFN73fOrYQQjBzVozGhApn9NUfDg fuQQ== X-Gm-Message-State: AJIora/VwR46wheGQAfbFj5jkqrVPeVk2ht9+Z5ZNeZE9tuIX+uWIm6m ZDXfDy/RimyjG3CfqoPr8oSzhY83WjSnI4smuXSjXQ== X-Google-Smtp-Source: AGRyM1udkVPlO63GfC4BLkNT9+dM2vQq6XSD4NXMR7yGY2lS9BL5p9z+pJY4uHpYS5xTpp/Nst2jDjRknGYXzO6pxHw= X-Received: by 2002:a25:a345:0:b0:66c:c670:6d13 with SMTP id d63-20020a25a345000000b0066cc6706d13mr39257526ybi.307.1657035777884; Tue, 05 Jul 2022 08:42:57 -0700 (PDT) MIME-Version: 1.0 References: <20220622162230.83474-1-kirill.shutemov@linux.intel.com> <20220622162230.83474-4-kirill.shutemov@linux.intel.com> In-Reply-To: <20220622162230.83474-4-kirill.shutemov@linux.intel.com> From: Alexander Potapenko Date: Tue, 5 Jul 2022 17:42:21 +0200 Message-ID: Subject: Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr() To: "Kirill A. Shutemov" Cc: Dave Hansen , Andy Lutomirski , Peter Zijlstra , "the arch/x86 maintainers" , Kostya Serebryany , Andrey Ryabinin , Andrey Konovalov , Dmitry Vyukov , "H . J . Lu" , Andi Kleen , Rick Edgecombe , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=AdcOA4QW; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf19.hostedemail.com: domain of glider@google.com designates 209.85.219.177 as permitted sender) smtp.mailfrom=glider@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1657035778; a=rsa-sha256; cv=none; b=C/tZgaonYorQOXkpHayySPBsIFjH+4KQg6VMK9s7YfzchhWrvmsbHTF5xG3xiB/xzxq37f /gEQgC2uEV5wurTjdpnzFPnVYkx41UuFpUgSiUkXOTnM0IAgfrFiBcrCx3PNhQ7B23qSTY mghiYI3loBcmiyXN+A/PU4sDt9rGWG4= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1657035778; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=kUzw94hBwwicZTDoD8iw9qTQlYL+xAA3YQavMnnyh1w=; b=Yoe7YuuF98b0FpsItKNJbpRiU2wbPM1PA38d+PVFN7yc5Xud6coBrKapFSw5LRPaQyDhjW 7r7UltnMhmmA32Aq77kZ35PU1M6zknvY09mkEIn7IgqjadDsBN6KYyUXhpyUoXcNnRLzrq DZY1U5KhooEdNh4+RHMPzU+GKWw7Yug= Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=AdcOA4QW; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf19.hostedemail.com: domain of glider@google.com designates 209.85.219.177 as permitted sender) smtp.mailfrom=glider@google.com X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: wd536khq99xw8kinf4wzfyjb1cyh7tqc X-Rspamd-Queue-Id: BCB6C1A0058 X-HE-Tag: 1657035778-303815 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: Kirill, > diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c > index feeb935a2299..abc096a68f05 100644 > --- a/lib/strnlen_user.c > +++ b/lib/strnlen_user.c > @@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count) > return 0; > > max_addr =3D TASK_SIZE_MAX; > - src_addr =3D (unsigned long)untagged_addr(str); > + src_addr =3D (unsigned long)untagged_addr(current->mm, str); In a downstream kernel with LAM disabled I'm seeing current->mm being NULL at this point, because strnlen_user() is being called by kdevtmpfs. IIUC current->mm is only guaranteed to be non-NULL in the userspace process context, whereas untagged_addr() may get called in random places. Am I missing something? --=20 Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Stra=C3=9Fe, 33 80636 M=C3=BCnchen Gesch=C3=A4ftsf=C3=BChrer: Paul Manicle, Liana Sebastian Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg