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=-11.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 6A514C433DF for ; Sun, 23 Aug 2020 00:49:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5258A207C3 for ; Sun, 23 Aug 2020 00:49:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725906AbgHWAtE (ORCPT ); Sat, 22 Aug 2020 20:49:04 -0400 Received: from netrider.rowland.org ([192.131.102.5]:48467 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1725770AbgHWAtE (ORCPT ); Sat, 22 Aug 2020 20:49:04 -0400 Received: (qmail 292705 invoked by uid 1000); 22 Aug 2020 20:49:03 -0400 Date: Sat, 22 Aug 2020 20:49:03 -0400 From: Alan Stern To: trix@redhat.com Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] usb: storage: initialize variable Message-ID: <20200823004903.GB292576@rowland.harvard.edu> References: <20200822211839.5117-1-trix@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200822211839.5117-1-trix@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Sat, Aug 22, 2020 at 02:18:39PM -0700, trix@redhat.com wrote: > From: Tom Rix > > clang static analysis reports this representative problem > > transport.c:495:15: warning: Assigned value is garbage or > undefined > length_left -= partial; > ^ ~~~~~~~ > partial is set only when usb_stor_bulk_transfer_sglist() > is successful. > > So initialize to partial to 0. > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Signed-off-by: Tom Rix > --- > drivers/usb/storage/transport.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c > index 238a8088e17f..ce920851b1f2 100644 > --- a/drivers/usb/storage/transport.c > +++ b/drivers/usb/storage/transport.c > @@ -461,7 +461,7 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe, > int usb_stor_bulk_srb(struct us_data* us, unsigned int pipe, > struct scsi_cmnd* srb) > { > - unsigned int partial; > + unsigned int partial = 0; > int result = usb_stor_bulk_transfer_sglist(us, pipe, scsi_sglist(srb), > scsi_sg_count(srb), scsi_bufflen(srb), > &partial); > @@ -484,7 +484,7 @@ int usb_stor_bulk_transfer_sg(struct us_data* us, unsigned int pipe, > void *buf, unsigned int length_left, int use_sg, int *residual) > { > int result; > - unsigned int partial; > + unsigned int partial = 0; > > /* are we scatter-gathering? */ > if (use_sg) { Yes, this is a bug. But the right way to fix it is to change usb_stor_bulk_transfer_sglist(): Make it store 0 to *act_len at the start. That way you change only one localized piece of code, instead of changing multiple callers and leaving a possibility of more errors being added in the future. Alan Stern