From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751747AbbIGNek (ORCPT ); Mon, 7 Sep 2015 09:34:40 -0400 Received: from mail-pa0-f43.google.com ([209.85.220.43]:33501 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750936AbbIGNei (ORCPT ); Mon, 7 Sep 2015 09:34:38 -0400 Date: Mon, 7 Sep 2015 22:33:32 +0900 From: Sergey Senozhatsky To: Luis Henriques Cc: Sergey Senozhatsky , Minchan Kim , Nitin Gupta , Sergey Senozhatsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH] zram: fix possible use after free in zcomp_create() Message-ID: <20150907133332.GA539@swordfish> References: <1441622033-8358-1-git-send-email-luis.henriques@canonical.com> <20150907111148.GB27956@swordfish> <20150907125343.GG10075@ares> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20150907125343.GG10075@ares> 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 13:53), Luis Henriques wrote: > > 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? > > > > Yep, that's probably a better solution. > > Acked-by: Luis Henriques > Oh, thanks. I don't mind if you will re-submit it; I just did minor changes to our fix. Or I can handle it. I'm OK with either way. Btw, did you hit that problem or you reviewed the code? -ss > Cheers, > -- > Luís > > > --- > > > > 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); > > } > > >