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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_IN_DEF_DKIM_WL 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 79A30C433DF for ; Thu, 4 Jun 2020 20:08:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 567FE207ED for ; Thu, 4 Jun 2020 20:08:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="M0mkpsLd" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729009AbgFDUI6 (ORCPT ); Thu, 4 Jun 2020 16:08:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49602 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728590AbgFDUI5 (ORCPT ); Thu, 4 Jun 2020 16:08:57 -0400 Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6C8F6C08C5C6 for ; Thu, 4 Jun 2020 13:08:57 -0700 (PDT) Received: by mail-pg1-x541.google.com with SMTP id p30so3985715pgl.11 for ; Thu, 04 Jun 2020 13:08:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=AFF1riO+rvi+JtGxWF5qzVLPXHH0Nzh8aZcDxBuji4s=; b=M0mkpsLd7B3310QKl3SLGg22ik2mXjNx5FY1vzJopMffJnCw8jRcmo9fV9LTIHikFp RUv7WnBJ6K5VaUslDx62awUaItJ+YKUKSU3/LS3bQT0QPBOUmH8h7pgLYyxlBLfTzZPU CwkTICvo+M0GUh+egz/pFlCv8tR424B81CNZ9aQO8/k4dMiV20ohQx7N7YX7tjfxxqqp JKfbJIsE+MYGNYLFN8gpzmr0Avp6j5x4qED0RF7A5OiE4WLh5w8/DvLwZz8GAkmSlO6c QbXytbk3xKeeMX1S4Xa0zICtEJbZ60RM6KlvqWwsKz3NAMy2eeUR9b8nqFf/OpAnG9F0 SQHw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=AFF1riO+rvi+JtGxWF5qzVLPXHH0Nzh8aZcDxBuji4s=; b=IRbx0EKlO2tI2WausEIqxgY/0rtEKlQ91yLiq684c0YJAXU3AZjnCJUQMd4dYp/zoX bCMAsz2vRYrWtAO9qwE4cSc5mqPNZFAHcu6vaIglZRJev16UsyFfMwkWqDlz29t1Jq6l CtLNAkdBlVCT4xgjie4exO4Mkn09Uvc1xsmeVv08rL6YooywJQKQcwYiyAR42FwlYQug MS2ENNdLpoCk2GXBqBlXrt+2n7FLsjhp724LbRTUVZD7Gd0jvLNAW75nviUhGUXWPKRf 2UDmEpTQnc0QfqCwwRtdGXxWwA02KDFxgbU0bkh9Ri2vKhPgbcAVLLrZB1nxvidQYsDe Fv0A== X-Gm-Message-State: AOAM530Q4++QDegIzYzGYr24ulClDhkET7ux+9c2rT7JOn9prQ1r/Og2 /OqXekQ1tc3q/0YA7QzCKrfTk1/gerGrrTpzKEiRGw== X-Google-Smtp-Source: ABdhPJxLMcvCCgSkDUjAgCX71OWizViN7uenmXgd4TZP4zed6Dsn/5qWQdcJBcIITrWPyVLL/7sbTfhjLEhVY3eJVkA= X-Received: by 2002:a63:5644:: with SMTP id g4mr5811569pgm.381.1591301336363; Thu, 04 Jun 2020 13:08:56 -0700 (PDT) MIME-Version: 1.0 References: <20200603233203.1695403-1-keescook@chromium.org> <20200603233203.1695403-4-keescook@chromium.org> In-Reply-To: <20200603233203.1695403-4-keescook@chromium.org> From: Nick Desaulniers Date: Thu, 4 Jun 2020 13:08:44 -0700 Message-ID: Subject: Re: [PATCH 03/10] b43: Remove uninitialized_var() usage To: Kees Cook Cc: LKML , Linus Torvalds , Miguel Ojeda , Alexander Potapenko , Joe Perches , Andy Whitcroft , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , drbd-dev@lists.linbit.com, linux-block@vger.kernel.org, b43-dev@lists.infradead.org, Network Development , linux-wireless , linux-ide@vger.kernel.org, linux-clk@vger.kernel.org, linux-spi@vger.kernel.org, Linux Memory Management List , clang-built-linux Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jun 3, 2020 at 4:32 PM Kees Cook wrote: > > Using uninitialized_var() is dangerous as it papers over real bugs[1] > (or can in the future), and suppresses unrelated compiler warnings (e.g. > "unused variable"). If the compiler thinks it is uninitialized, either > simply initialize the variable or make compiler changes. As a precursor > to removing[2] this[3] macro[4], just initialize this variable to NULL, > and make the (unreachable!) code do a conditional test. > > [1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/ > [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ > [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ > [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ > > Signed-off-by: Kees Cook > --- > drivers/net/wireless/broadcom/b43/phy_n.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/wireless/broadcom/b43/phy_n.c b/drivers/net/wireless/broadcom/b43/phy_n.c > index d3c001fa8eb4..88cdcea10d61 100644 > --- a/drivers/net/wireless/broadcom/b43/phy_n.c > +++ b/drivers/net/wireless/broadcom/b43/phy_n.c > @@ -4222,7 +4222,7 @@ static void b43_nphy_tx_gain_table_upload(struct b43_wldev *dev) The TODOs and `#if 0` in this function are concerning. It looks like `rf_pwr_offset_table` is only used when `phy->rev` is >=7 && < 19. Further, the loop has a case for `phy->rev >= 19` but we would have returned earlier if that was the case. > u32 rfpwr_offset; > u8 pga_gain, pad_gain; > int i; > - const s16 *uninitialized_var(rf_pwr_offset_table); > + const s16 *rf_pwr_offset_table = NULL; > > table = b43_nphy_get_tx_gain_table(dev); > if (!table) > @@ -4256,9 +4256,13 @@ static void b43_nphy_tx_gain_table_upload(struct b43_wldev *dev) > pga_gain = (table[i] >> 24) & 0xf; > pad_gain = (table[i] >> 19) & 0x1f; > if (b43_current_band(dev->wl) == NL80211_BAND_2GHZ) > - rfpwr_offset = rf_pwr_offset_table[pad_gain]; > + rfpwr_offset = rf_pwr_offset_table > + ? rf_pwr_offset_table[pad_gain] > + : 0; > else > - rfpwr_offset = rf_pwr_offset_table[pga_gain]; > + rfpwr_offset = rf_pwr_offset_table > + ? rf_pwr_offset_table[pga_gain] > + : 0; The code is trying to check `phy->rev >= 7 && phy->rev < 19` once before the loop, then set `rf_pwr_offset_table`, so having another conditional on `rf_pwr_offset_table` in the loop is unnecessary. I'm ok with initializing it to `NULL`, but I'm not sure the conditional check is necessary. Do you get a compiler warning otherwise? > } else { > pga_gain = (table[i] >> 24) & 0xF; > if (b43_current_band(dev->wl) == NL80211_BAND_2GHZ) > -- > 2.25.1 > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200603233203.1695403-4-keescook%40chromium.org. -- Thanks, ~Nick Desaulniers