From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx01.omp.ru (mx01.omp.ru [90.154.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 06D5D36A037 for ; Sat, 31 Jan 2026 19:42:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.154.21.10 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769888529; cv=none; b=prhfFQ1vnnpyaox3HNtxIGIhlcvNzc+cMiln7Izwh3UhtdmHGncwYZnboPo5dtoJn8dl9hTPeDIQ0PwjR0iyQNELiSSkJas90A6ES8CjwXp6OZiV5gHmhUZrK+VLHz4eDoy5aHxn58FXn97pdRdWS/5uX/M18alkfptjDoyumek= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769888529; c=relaxed/simple; bh=/jUI5JcVJ2bizjGrT6BScoB72fcEhv41slBYBNKuH3Q=; h=Message-ID:Date:MIME-Version:Subject:From:To:CC:References: In-Reply-To:Content-Type; b=PpRrk+i8SA5Y06h8lqN8gXamQPopFFPD5ret1scudBBbFJ5/vVaf4I6VS9OthXSCEJIkwzinnoyUwFrc8CdROgssjd9wm86+d8v/LLTUt0xJT5yFzP7iZPpBH11N00Btrwp91LawtFbRiut4zEKwKTol3ldHwq/2P14TG6j3v0Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=omp.ru; spf=pass smtp.mailfrom=omp.ru; arc=none smtp.client-ip=90.154.21.10 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=omp.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=omp.ru Received: from [192.168.2.104] (213.87.153.244) by msexch01.omp.ru (10.188.4.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.1258.12; Sat, 31 Jan 2026 22:26:45 +0300 Message-ID: Date: Sat, 31 Jan 2026 22:26:44 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fixp-arith: prevent division by zero in fixp_sin32_rad() From: Sergey Shtylyov To: Roman Smirnov , CC: References: <20240312094852.15400-1-r.smirnov@omp.ru> Content-Language: en-US Organization: Open Mobile Platform In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-ClientProxiedBy: msexch01.omp.ru (10.188.4.12) To msexch01.omp.ru (10.188.4.12) X-KSE-ServerInfo: msexch01.omp.ru, 9 X-KSE-AntiSpam-Interceptor-Info: scan successful X-KSE-AntiSpam-Version: 6.1.1, Database issued on: 01/31/2026 19:15:53 X-KSE-AntiSpam-Status: KAS_STATUS_NOT_DETECTED X-KSE-AntiSpam-Method: none X-KSE-AntiSpam-Rate: 19 X-KSE-AntiSpam-Info: Lua profiles 200014 [Jan 31 2026] X-KSE-AntiSpam-Info: Version: 6.1.1.20 X-KSE-AntiSpam-Info: Envelope from: s.shtylyov@omp.ru X-KSE-AntiSpam-Info: LuaCore: 86 0.3.86 47cb2a3d3f5c7e795bff2d0998e8c196722872ab X-KSE-AntiSpam-Info: {rep_avail} X-KSE-AntiSpam-Info: {SMTP from is not routable} X-KSE-AntiSpam-Info: {Found in DNSBL: 213.87.153.244 in (user) dbl.spamhaus.org} X-KSE-AntiSpam-Info: omp.ru:7.1.1;d41d8cd98f00b204e9800998ecf8427e.com:7.1.1;127.0.0.199:7.1.2 X-KSE-AntiSpam-Info: {Tracking_ip_hunter} X-KSE-AntiSpam-Info: FromAlignment: s X-KSE-AntiSpam-Info: ApMailHostAddress: 213.87.153.244 X-KSE-AntiSpam-Info: {DNS response errors} X-KSE-AntiSpam-Info: Rate: 19 X-KSE-AntiSpam-Info: Status: not_detected X-KSE-AntiSpam-Info: Method: none X-KSE-AntiSpam-Info: Auth:dmarc=temperror header.from=omp.ru;spf=temperror smtp.mailfrom=omp.ru;dkim=none X-KSE-Antiphishing-Info: Clean X-KSE-Antiphishing-ScanningType: Heuristic X-KSE-Antiphishing-Method: None X-KSE-Antiphishing-Bases: 01/31/2026 19:17:00 X-KSE-Antivirus-Interceptor-Info: scan successful X-KSE-Antivirus-Info: Clean, bases: 1/31/2026 2:14:00 PM X-KSE-Attachment-Filter-Triggered-Rules: Clean X-KSE-Attachment-Filter-Triggered-Filters: Clean X-KSE-BulkMessagesFiltering-Scan-Result: InTheLimit On 3/13/24 9:23 PM, Sergey Shtylyov wrote: [...] >> The parameter twopi can have a zero value. It is necessary >> to prevent division by zero. >> >> Found by Linux Verification Center (linuxtesting.org) with Svace. >> >> Signed-off-by: Roman Smirnov >> --- >> include/linux/fixp-arith.h | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/include/linux/fixp-arith.h b/include/linux/fixp-arith.h >> index e485fb0c1201..434eee8bd9ef 100644 >> --- a/include/linux/fixp-arith.h >> +++ b/include/linux/fixp-arith.h >> @@ -118,8 +118,9 @@ static inline s32 fixp_sin32_rad(u32 radians, u32 twopi) >> >> /* >> * Avoid too large values for twopi, as we don't want overflows. >> + * Also prevent division by zero. >> */ >> - BUG_ON(twopi > 1 << 18); >> + BUG_ON(!twopi || twopi > 1 << 18); > > Not really sure ATM that BUG_ON() is better than division by 0 > (which should cause exception 0 on x86 but I'm not sure about e.g. > ARM32/64)... Now I know what happens there: on arch/arm/ an pr_err() will be called followed by dump_stack(); on arch/arm64/ division instruction will silently yield 0 result... >> >> degrees = (radians * 360) / twopi; >> tmp = radians - (degrees * twopi) / 360; >> > > Reviewed-by: Sergey Shtylyov The patch does seem legitimate... ]...] MBR, Sergey