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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_MUTT autolearn=ham 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 51FC5C282E3 for ; Mon, 27 May 2019 01:49:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2E8652075C for ; Mon, 27 May 2019 01:49:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726175AbfE0BtR (ORCPT ); Sun, 26 May 2019 21:49:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37788 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725867AbfE0BtR (ORCPT ); Sun, 26 May 2019 21:49:17 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 349AD3092664; Mon, 27 May 2019 01:49:17 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DC4D15C3FD; Mon, 27 May 2019 01:49:14 +0000 (UTC) Date: Sun, 26 May 2019 21:49:14 -0400 From: Mike Snitzer To: Gen Zhang Cc: agk@redhat.com, dm-devel@redhat.com, linux-kernel@vger.kernel.org Subject: Re: dm-region-hash: fix a missing-check bug in __rh_alloc() Message-ID: <20190527014913.GA10098@redhat.com> References: <20190527005034.GA16907@zhanggen-UX430UQ> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190527005034.GA16907@zhanggen-UX430UQ> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 27 May 2019 01:49:17 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 26 2019 at 8:50pm -0400, Gen Zhang wrote: > In function __rh_alloc(), the pointer nreg is allocated a memory space > via kmalloc(). And it is used in the following codes. However, when > there is a memory allocation error, kmalloc() fails. Thus null pointer > dereference may happen. And it will cause the kernel to crash. Therefore, > we should check the return value and handle the error. > Further, in __rh_find(), we should also check the return value and > handle the error. > > Signed-off-by: Gen Zhang > --- > diff --git a/drivers/md/dm-region-hash.c b/drivers/md/dm-region-hash.c > index 1f76045..2fa1641 100644 > --- a/drivers/md/dm-region-hash.c > +++ b/drivers/md/dm-region-hash.c > @@ -290,8 +290,11 @@ static struct dm_region *__rh_alloc(struct dm_region_hash *rh, region_t region) > struct dm_region *reg, *nreg; > > nreg = mempool_alloc(&rh->region_pool, GFP_ATOMIC); > - if (unlikely(!nreg)) > + if (unlikely(!nreg)) { > nreg = kmalloc(sizeof(*nreg), GFP_NOIO | __GFP_NOFAIL); > + if (!nreg) > + return NULL; > + } > > nreg->state = rh->log->type->in_sync(rh->log, region, 1) ? > DM_RH_CLEAN : DM_RH_NOSYNC; This patch isn't needed. __GFP_NOFAIL means the allocation won't fail. And there are many other users of __GFP_NOFAIL that don't check for failure. Mike