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 E1368C433E3 for ; Tue, 25 Aug 2020 00:36:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CADD42074D for ; Tue, 25 Aug 2020 00:36:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728087AbgHYAge (ORCPT ); Mon, 24 Aug 2020 20:36:34 -0400 Received: from netrider.rowland.org ([192.131.102.5]:41795 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1728073AbgHYAge (ORCPT ); Mon, 24 Aug 2020 20:36:34 -0400 Received: (qmail 350852 invoked by uid 1000); 24 Aug 2020 20:36:33 -0400 Date: Mon, 24 Aug 2020 20:36:33 -0400 From: Alan Stern To: Tom Rix Cc: Vito Caputo , gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, usb-storage@lists.one-eyed-alien.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] usb: storage: initialize variable Message-ID: <20200825003633.GB350601@rowland.harvard.edu> References: <20200824211027.11543-1-trix@redhat.com> <20200824211839.6c7m7yhgd7ffq3g3@shells.gnugeneration.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, Aug 24, 2020 at 02:31:01PM -0700, Tom Rix wrote: > > On 8/24/20 2:18 PM, Vito Caputo wrote: > > On Mon, Aug 24, 2020 at 02:10:27PM -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 set partial on entry to 0. > >> > >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > >> Signed-off-by: Tom Rix > >> --- > >> drivers/usb/storage/transport.c | 3 +++ > >> 1 file changed, 3 insertions(+) > >> > >> diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c > >> index 238a8088e17f..044429717dcc 100644 > >> --- a/drivers/usb/storage/transport.c > >> +++ b/drivers/usb/storage/transport.c > >> @@ -414,6 +414,9 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe, > >> { > >> int result; > >> > >> + if (act_len) > >> + *act_len = 0; > >> + > >> /* don't submit s-g requests during abort processing */ > >> if (test_bit(US_FLIDX_ABORTING, &us->dflags)) > >> return USB_STOR_XFER_ERROR; > > At a glance this seems odd to me. If the caller insists on ignoring > > the return value, shouldn't it just initialize partial to zero? > > > > In my experience it's generally frowned upon for functions to store > > results in error paths. > > Then maybe v1 is more appropriate. > > Else i can spin a v3. > > My preference is v1 as it doesn't add any runtime if-checks. If you really want to get rid of the runtime check (both the one you added and the one already present), you can audit all the callers of this routine to make certain that none of them pass a NULL pointer for act_len. Alan Stern