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 B4E1CC433F5 for ; Tue, 26 Apr 2022 21:06:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 08E946B0073; Tue, 26 Apr 2022 17:06:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 03E5C6B0074; Tue, 26 Apr 2022 17:06:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E48396B0075; Tue, 26 Apr 2022 17:06:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.27]) by kanga.kvack.org (Postfix) with ESMTP id D20BE6B0073 for ; Tue, 26 Apr 2022 17:06:44 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 9DEBD80FA7 for ; Tue, 26 Apr 2022 21:06:44 +0000 (UTC) X-FDA: 79400264328.03.1D3CB7F Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf15.hostedemail.com (Postfix) with ESMTP id 5FFBCA004C for ; Tue, 26 Apr 2022 21:06:39 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2802B6160D; Tue, 26 Apr 2022 21:06:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 436CFC385A4; Tue, 26 Apr 2022 21:06:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1651007202; bh=d4vNieU9C1R0ukFjOzDog7Jl8A2oEUBzKVDoPNTk3nM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=AXxJUn48WsZtYjaYH0DI8pHLDlx7PBvGooyg/6vOF38p1y+7q1zK+T7jRi3mLFiGa KdEp1mW7w514E4UPK26+Bm+gp7OHsUr65lEFgt+a0ENPg6Gzks5Iqqzrp3ueHC14rF LEiUkPPhvZzEkEGXIGeVTbve4XAKCs7oOKmxqqjg= Date: Tue, 26 Apr 2022 14:06:41 -0700 From: Andrew Morton To: Matthew Wilcox Cc: Wan Jiabing , Vlastimil Babka , David Howells , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Julia Lawall Subject: Re: [PATCH] mm/filemap: Fix NULL pointer dereference in pagecache_get_page Message-Id: <20220426140641.cc78a429e1fa32ed0e15520b@linux-foundation.org> In-Reply-To: References: <20220426082549.590899-1-wanjiabing@vivo.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 5FFBCA004C X-Stat-Signature: utgry3r3g4sy1zzgpnyxjdpsds5zsbgh Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=AXxJUn48; spf=pass (imf15.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-HE-Tag: 1651007199-128413 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, 26 Apr 2022 13:08:08 +0100 Matthew Wilcox wrote: > On Tue, Apr 26, 2022 at 04:25:48PM +0800, Wan Jiabing wrote: > > Fix following coccicheck error: > > mm/folio-compat.c:128:17-21: ERROR: folio is NULL but dereferenced. > > folio = __filemap_get_folio(mapping, index, fgp_flags, gfp); > > - if ((fgp_flags & FGP_HEAD) || !folio || xa_is_value(folio)) > > + if (!folio) > > + return NULL; > > + if ((fgp_flags & FGP_HEAD) || xa_is_value(folio)) > > return &folio->page; > > That doesn't dereference the folio. Coccicheck is wrong. Doing return &(0->page); is a rather obscure way of doing `return NULL;'. I agree the patch doesn't fix anything, but it results in saner-looking code?