From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933068AbaLBM7c (ORCPT ); Tue, 2 Dec 2014 07:59:32 -0500 Received: from e06smtp14.uk.ibm.com ([195.75.94.110]:37819 "EHLO e06smtp14.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932998AbaLBM73 (ORCPT ); Tue, 2 Dec 2014 07:59:29 -0500 Subject: Re: [PATCH] misc: genwqe: check for error from get_user_pages_fast() From: Frank Haverkamp Reply-To: haver@linux.vnet.ibm.com To: Ian Abbott Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Thadeu Lima De Souza Cascardo In-Reply-To: <1415291019-6178-1-git-send-email-abbotti@mev.co.uk> References: <1415291019-6178-1-git-send-email-abbotti@mev.co.uk> Content-Type: text/plain; charset="UTF-8" Organization: IBM Date: Tue, 02 Dec 2014 13:59:20 +0100 Message-ID: <1417525160.2010.4.camel@oc7383187364.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-30.el6) Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14120212-0017-0000-0000-0000020E921F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ian, thanks for reviewing our code and sorry for not answering immediately. Am Donnerstag, den 06.11.2014, 16:23 +0000 schrieb Ian Abbott: > `genwqe_user_vmap()` calls `get_user_pages_fast()` and if the return > value is less than the number of pages requested, it frees the pages and > returns an error (`-EFAULT`). However, it fails to consider a negative > error return value from `get_user_pages_fast()`. In that case, the test > `if (rc < m->nr_pages)` will be false (due to promotion of `rc` to a > large `unsigned int`) and the code will continue on to call > `genwqe_map_pages()` with an invalid list of page pointers. Fix it by > bailing out if `get_user_pages_fast()` returns a negative error value. True. Did you find this by manual inspection of the code or did you use tools to figure it out? > > Signed-off-by: Ian Abbott > Cc: # 3.14.x # 3.15.x # 3.16.x # 3.17.x > --- > drivers/misc/genwqe/card_utils.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/misc/genwqe/card_utils.c b/drivers/misc/genwqe/card_utils.c > index 7cb3b7e..1ca94e6 100644 > --- a/drivers/misc/genwqe/card_utils.c > +++ b/drivers/misc/genwqe/card_utils.c > @@ -590,6 +590,8 @@ int genwqe_user_vmap(struct genwqe_dev *cd, struct dma_mapping *m, void *uaddr, > m->nr_pages, > 1, /* write by caller */ > m->page_list); /* ptrs to pages */ > + if (rc < 0) > + goto fail_get_user_pages; > > /* assumption: get_user_pages can be killed by signals. */ > if (rc < m->nr_pages) { Regards Frank Acked-by: Frank Haverkamp