From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751069AbbIGLLK (ORCPT ); Mon, 7 Sep 2015 07:11:10 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:32839 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750752AbbIGLLI (ORCPT ); Mon, 7 Sep 2015 07:11:08 -0400 Date: Mon, 7 Sep 2015 20:11:48 +0900 From: Sergey Senozhatsky To: Luis Henriques Cc: Minchan Kim , Nitin Gupta , Sergey Senozhatsky , Sergey Senozhatsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH] zram: fix possible use after free in zcomp_create() Message-ID: <20150907111148.GB27956@swordfish> References: <1441622033-8358-1-git-send-email-luis.henriques@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1441622033-8358-1-git-send-email-luis.henriques@canonical.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (09/07/15 11:33), Luis Henriques wrote: > zcomp_create() verifies the success of zcomp_strm_{multi,siggle}_create() > through comp->stream, which can potentially be pointing to memory that was > freed if these functions returned an error. > good catch. we probably better start checking the zcomp_strm_multi_create()/ zcomp_strm_single_create() status in zcomp_create(); that's much more obvious and that's why we return it in the first place. what do you think? --- drivers/block/zram/zcomp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c index 3456d5a..16bbc8c 100644 --- a/drivers/block/zram/zcomp.c +++ b/drivers/block/zram/zcomp.c @@ -360,6 +360,7 @@ struct zcomp *zcomp_create(const char *compress, int max_strm) { struct zcomp *comp; struct zcomp_backend *backend; + int ret; backend = find_backend(compress); if (!backend) @@ -371,10 +372,10 @@ struct zcomp *zcomp_create(const char *compress, int max_strm) comp->backend = backend; if (max_strm > 1) - zcomp_strm_multi_create(comp, max_strm); + ret = zcomp_strm_multi_create(comp, max_strm); else - zcomp_strm_single_create(comp); - if (!comp->stream) { + ret = zcomp_strm_single_create(comp); + if (ret != 0) { kfree(comp); return ERR_PTR(-ENOMEM); }