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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 60CACC433E0 for ; Fri, 22 Jan 2021 01:35:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BA4A4239EF for ; Fri, 22 Jan 2021 01:35:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BA4A4239EF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D21316B0006; Thu, 21 Jan 2021 20:35:41 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id CD1506B0007; Thu, 21 Jan 2021 20:35:41 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BE7356B0008; Thu, 21 Jan 2021 20:35:41 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0182.hostedemail.com [216.40.44.182]) by kanga.kvack.org (Postfix) with ESMTP id A6CB16B0006 for ; Thu, 21 Jan 2021 20:35:41 -0500 (EST) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 6AACA5833 for ; Fri, 22 Jan 2021 01:35:41 +0000 (UTC) X-FDA: 77731694082.23.music77_46038b827567 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin23.hostedemail.com (Postfix) with ESMTP id 49AA537604 for ; Fri, 22 Jan 2021 01:35:41 +0000 (UTC) X-HE-Tag: music77_46038b827567 X-Filterd-Recvd-Size: 2126 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Fri, 22 Jan 2021 01:35:40 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 726592389F; Fri, 22 Jan 2021 01:35:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1611279339; bh=TSUs67BnHPXyVp/+RYOtdDwgklU6bi0E5ra79hh+iKc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=HY5PTbWiIiDr8VRe+QBYvJO96CSUViAY3yOsUWU14NBit1o+eHwE1sEK4af1AoUpw IrHNQxOU9yWw5YvFUSfAC8EkvKdYGrYRmJ6gD1U41y/ZyLhWsI4uh3wMMK/Upaf+ec LrtHNXJb0/Cny5WS0yK6IJEbelabayLc5XmUFPYs= Date: Thu, 21 Jan 2021 17:35:38 -0800 From: Andrew Morton To: Tetsuo Handa Cc: linux-mm@kvack.org Subject: Re: [PATCH v2] mm: memdup_user*() should use same gfp flags Message-Id: <20210121173538.166e8b27408d4525360fbb70@linux-foundation.org> In-Reply-To: <20210120103436.11830-1-penguin-kernel@I-love.SAKURA.ne.jp> References: <20210120041843.5090-1-penguin-kernel@I-love.SAKURA.ne.jp> <20210120103436.11830-1-penguin-kernel@I-love.SAKURA.ne.jp> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Wed, 20 Jan 2021 19:34:36 +0900 Tetsuo Handa wrote: > syzbot is reporting that memdup_user_nul() which receives user-controlled > size (which can be up to (INT_MAX & PAGE_MASK)) via vfs_write() will hit > order >= MAX_ORDER path [1]. > > Let's add __GFP_NOWARN to memdup_user_nul() as with commit 6c8fcc096be9d02f > ("mm: don't let userspace spam allocations warnings"). Also use GFP_USER as > with commit 6c2c97a24f096e32 ("memdup_user(): switch to GFP_USER"). That commit failed to explain why a switch to GFP_USER was performed, so that commit isn't a good substitute for an explanation of this change. So... please fully describe the reason for this change right here in this patch's changelog.