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 C052FC433EF for ; Thu, 24 Mar 2022 21:44:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4BD606B0071; Thu, 24 Mar 2022 17:44:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 446DF6B0073; Thu, 24 Mar 2022 17:44:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2E63A6B0074; Thu, 24 Mar 2022 17:44:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0148.hostedemail.com [216.40.44.148]) by kanga.kvack.org (Postfix) with ESMTP id 1A8F96B0071 for ; Thu, 24 Mar 2022 17:44:58 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id CCCC31827C17D for ; Thu, 24 Mar 2022 21:44:57 +0000 (UTC) X-FDA: 79280610234.17.FCE8046 Received: from mail-io1-f42.google.com (mail-io1-f42.google.com [209.85.166.42]) by imf24.hostedemail.com (Postfix) with ESMTP id 54399180041 for ; Thu, 24 Mar 2022 21:44:57 +0000 (UTC) Received: by mail-io1-f42.google.com with SMTP id h63so6957462iof.12 for ; Thu, 24 Mar 2022 14:44:57 -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; bh=NtG3L3i2VNWzLKZCzuXCjQJQZ/iQPSa3QxfocCII+yI=; b=QiXk2bRrt9r2iy2pw39Ur0S1CksPSEVIavay+B5XCLlr32bHYrl+Jg7S1Wz9sJJddl SfdJh5KvOpCXlLl6D0qlljbm2QqG1ZimdlJGZ+kY9v0tqLOFLckFYG0DIgSDejmgHFOu rvJt10zs3T+Zi/e0PitYFXusD6ngNFenflicfM+z7BGnOC4QWS34JsIgWTg7/zkzy/ce 7yxmWbt6nH+726Ctq2wDyguUw9/BW1sCSX+QZ396esY35eMesUxgt4VlPFEdEaDT7vkL 8gnnaadz7PnCccOhffngbcdUOLtLr14uCeS7R2+XRp2J/I3wNU3R3yqCdjO2F3zsGKm6 uu3A== 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; bh=NtG3L3i2VNWzLKZCzuXCjQJQZ/iQPSa3QxfocCII+yI=; b=URhYL3HMYBVEzfKTn+8rry45Y3RywGR62GKB1nWbPLKr0mVMFhIAUreGmVttdrB6l/ bHPhMlrmrYwt7XnTSs0Dh3Hy1axPuQKM+urI4JU3QaWxenxWB449Zb3u818/iKRwG2B2 RInEOCp1wi3GRo6PqgiEuEZ7/wOCpUjiucy39NpLcYLz8qLSaj1INXN4BZ0CbOHSHjrf sYy29HTMBnaHO/o6YJ59pqCPC7YnBQRq3MBcottaqb3lZDMh/SyGiC4OnA1T49NbNQTv IwQ7unJyEr6tYUNkv4klwRfz7GMGbxIeiIQTmH1kLeBDGOd5bPbLq/PE7SyGhwInDRIq 0RLQ== X-Gm-Message-State: AOAM532z7+LkFVEqb2upEP+qVbSJfcPCxj55/N8r5p7C/BBE5MQclnLi GhAPjnKTb9t9aBxet1Bjxonzf87VqcbA90WXh6k1xQ== X-Google-Smtp-Source: ABdhPJzWHqISwWQ+GxG0Zg2dYghqEE6/RmqQZ/aiWq9FM5RxmFzYXqerGBEFOf6FUUsx7Gpn4GC0i7gIFHccilOldj8= X-Received: by 2002:a05:6602:1493:b0:649:1890:cffd with SMTP id a19-20020a056602149300b006491890cffdmr3907876iow.167.1648158296431; Thu, 24 Mar 2022 14:44:56 -0700 (PDT) MIME-Version: 1.0 References: <20220324210909.1843814-1-axelrasmussen@google.com> In-Reply-To: From: Axel Rasmussen Date: Thu, 24 Mar 2022 14:44:20 -0700 Message-ID: Subject: Re: [PATCH] mm/secretmem: fix panic when growing a memfd_secret To: Matthew Wilcox Cc: Andrew Morton , Mike Rapoport , Linux MM , LKML , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Stat-Signature: 1i8jp5b5dqqar6rucq68gbiyg36qbwqs Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=QiXk2bRr; spf=pass (imf24.hostedemail.com: domain of axelrasmussen@google.com designates 209.85.166.42 as permitted sender) smtp.mailfrom=axelrasmussen@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 54399180041 X-HE-Tag: 1648158297-200311 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000046, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 24, 2022 at 2:33 PM Matthew Wilcox wrote: > > On Thu, Mar 24, 2022 at 02:09:09PM -0700, Axel Rasmussen wrote: > > This patch avoids the panic by implementing a custom setattr for > > memfd_secret, which detects resizes specifically (setting the size for > > the first time works just fine, since there are no existing pages to try > > to zero), and rejects them as not supported (ENOTSUP). > > Isn't ENOTTY the normal return value for this? Or even ENOSYS? I'm unsure. Since errno(3) says ENOTTY means "Inappropriate I/O control operation" that makes me think it's meant to be used only for ioctls? I tried ENOSYS, but checkpatch warns me it's meant to be used for "invalid syscall nr" and nothing else. ENOTSUP / ENOTSUPP / EOPNOTSUPP all have their own share of weirdnesses too, though. There's the whole ENOTSUP / ENOTSUPP mess, and then also the fact that glibc says ENOTSUP == EOPNOTSUPP, whereas POSIX says EOPNOTSUPP should be distinct and used specifically for sockets...