From patchwork Mon Nov 27 01:35:13 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Su Hui X-Patchwork-Id: 748060 Authentication-Results: smtp.subspace.kernel.org; dkim=none Received: from mail.nfschina.com (unknown [42.101.60.195]) by lindbergh.monkeyblade.net (Postfix) with SMTP id 91395CB; Sun, 26 Nov 2023 17:35:54 -0800 (PST) Received: from localhost.localdomain (unknown [180.167.10.98]) by mail.nfschina.com (Maildata Gateway V2.8.8) with ESMTPSA id B7BBF6018CCDB; Mon, 27 Nov 2023 09:35:40 +0800 (CST) X-MD-Sfrom: suhui@nfschina.com X-MD-SrcIP: 180.167.10.98 From: Su Hui To: pkshih@realtek.com, dan.carpenter@linaro.org, kvalo@kernel.org, nathan@kernel.org, ndesaulniers@google.com, trix@redhat.com Cc: Su Hui , lizetao1@huawei.com, linville@tuxdriver.com, Larry.Finger@lwfinger.net, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, kernel-janitors@vger.kernel.org Subject: [PATCH wireless-next v3 2/2] wifi: rtlwifi: rtl8821ae: phy: fix an undefined bitwise shift behavior Date: Mon, 27 Nov 2023 09:35:13 +0800 Message-Id: <20231127013511.26694-2-suhui@nfschina.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20231127013511.26694-1-suhui@nfschina.com> Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Clang staic checker warning: drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c:184:49: The result of the left shift is undefined due to shifting by '32', which is greater or equal to the width of type 'u32'. [core.UndefinedBinaryOperatorResult] If the value of the right operand is negative or is greater than or equal to the width of the promoted left operand, the behavior is undefined.[1][2] For example, when using different gcc's compilation optimizaation options (-O0 or -O2), the result of '(u32)data << 32' is different. One is 0, the other is old value of data. Let _rtl8821ae_phy_calculate_bit_shift()'s return value less than 32 to fix this problem. Warn if bitmask is zero. [1]:https://stackoverflow.com/questions/11270492/what-does-the-c- standard-say-about-bitshifting-more-bits-than-the-width-of-type [2]:https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf Fixes: 21e4b0726dc6 ("rtlwifi: rtl8821ae: Move driver from staging to regular tree") Signed-off-by: Su Hui --- v3: - use __ffs() and make code briefer. (Thanks to Ping-Ke) v2: - fix the subject prefix problem - silence the warning by not return 32 bits rather than adding a type cast.(Thanks to Dan and Ping-Ke) drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c index 6df270e29e66..68c3fb0395ce 100644 --- a/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c +++ b/drivers/net/wireless/realtek/rtlwifi/rtl8821ae/phy.c @@ -29,9 +29,10 @@ static void _rtl8821ae_phy_rf_serial_write(struct ieee80211_hw *hw, u32 data); static u32 _rtl8821ae_phy_calculate_bit_shift(u32 bitmask) { - u32 i = ffs(bitmask); + if (WARN_ON_ONCE(!bitmask)) + return 0; - return i ? i - 1 : 32; + return __ffs(bitmask); } static bool _rtl8821ae_phy_bb8821a_config_parafile(struct ieee80211_hw *hw); /*static bool _rtl8812ae_phy_config_mac_with_headerfile(struct ieee80211_hw *hw);*/