From patchwork Tue Oct 11 13:04:28 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Paul Zhang X-Patchwork-Id: 614556 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 34A94C433F5 for ; Tue, 11 Oct 2022 13:05:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229900AbiJKNFQ (ORCPT ); Tue, 11 Oct 2022 09:05:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229910AbiJKNFN (ORCPT ); Tue, 11 Oct 2022 09:05:13 -0400 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D49701FCE6 for ; Tue, 11 Oct 2022 06:05:10 -0700 (PDT) Received: from pps.filterd (m0279873.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 29BBjKB6019254; Tue, 11 Oct 2022 13:05:08 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h=from : to : cc : subject : date : message-id : mime-version : content-type : content-transfer-encoding; s=qcppdkim1; bh=I1/gCtkfa7CgIRoxO3wfAR33NNRUjl2+/cjtCGvu19w=; b=GQAAUXJQTm37PnX+sDV7uHTfTAiPrabjbO4FEmxjmJ5EczBGpuOUII7vD9AfWfuWHAXq H1Mt2ezRV7BKWwCCv3MFbp7f/6PYoqDlDK17vtZy5FyBkjGlqzsb1vgWfAX8Ytr6zVr4 S/8MVrCdQD0QSNgoXwqf3kBwartZwUNVyL1TP8cgsZKbMrxBMyeo3k1SWAiulPT4cwii BJdig0XOEK+6uNx5FwJqIN2oYbxdyXT4vPCchHSJQtI6gs9xzcv2YAEwaxybuZ/EzozZ vCF2G8cN8iIdDfBu2lRLqu0QQ/ZV+fEKJMVoHpd8TdciwnmqKOUJrXZzVyGna+Yl0310 Uw== Received: from nalasppmta04.qualcomm.com (Global_NAT1.qualcomm.com [129.46.96.20]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 3k4rx4t5da-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 11 Oct 2022 13:05:07 +0000 Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA04.qualcomm.com (8.17.1.5/8.17.1.5) with ESMTPS id 29BD56x1012919 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 11 Oct 2022 13:05:06 GMT Received: from paulz-gv.qualcomm.com (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.29; Tue, 11 Oct 2022 06:05:05 -0700 From: Paul Zhang To: CC: Subject: [PATCH v1] cfg80211: Fix bitrates overflow issue Date: Tue, 11 Oct 2022 21:04:28 +0800 Message-ID: <1665493468-24774-1-git-send-email-quic_paulz@quicinc.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-GUID: QD1cMWxSzdyJfFD_v-dQu27OxNa9DtpV X-Proofpoint-ORIG-GUID: QD1cMWxSzdyJfFD_v-dQu27OxNa9DtpV X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.895,Hydra:6.0.545,FMLib:17.11.122.1 definitions=2022-10-11_07,2022-10-11_02,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 spamscore=0 mlxlogscore=707 impostorscore=0 phishscore=0 adultscore=0 clxscore=1011 malwarescore=0 bulkscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2209130000 definitions=main-2210110074 Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org When invoking function cfg80211_calculate_bitrate_eht about (320 MHz, EHT-MCS 13, EHT-NSS 2, EHT-GI 0), which means the parameters as flags: 0x80, bw: 7, mcs: 13, eht_gi: 0, nss: 2, this formula (result * rate->nss) will overflow and causes the returned bitrate to be 3959 when it should be 57646. Here is the explanation: u64 tmp; u32 result; … /* tmp = result = 4 * rates_996[0] * = 4 * 480388888 = 0x72889c60 */ tmp = result; /* tmp = 0x72889c60 * 6144 = 0xabccea90000 */ tmp *= SCALE; /* tmp = 0xabccea90000 / mcs_divisors[13] * = 0xabccea90000 / 5120 = 0x8970bba6 */ do_div(tmp, mcs_divisors[rate->mcs]); /* result = 0x8970bba6 */ result = tmp; /* normally (result * rate->nss) = 0x8970bba6 * 2 = 0x112e1774c, * but since result is u32, (result * rate->nss) = 0x12e1774c, * overflow happens and it loses the highest bit. * Then result = 0x12e1774c / 8 = 39595753, */ result = (result * rate->nss) / 8; Signed-off-by: Paul Zhang --- net/wireless/util.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/wireless/util.c b/net/wireless/util.c index f09d528..59d4947 100644 --- a/net/wireless/util.c +++ b/net/wireless/util.c @@ -1557,10 +1557,12 @@ static u32 cfg80211_calculate_bitrate_eht(struct rate_info *rate) tmp = result; tmp *= SCALE; do_div(tmp, mcs_divisors[rate->mcs]); - result = tmp; /* and take NSS */ - result = (result * rate->nss) / 8; + tmp *= rate->nss; + do_div(tmp, 8); + + result = tmp; return result / 10000; }