From patchwork Tue Dec 15 09:20:30 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 1416343 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4CwCSm23QDz9s0b for ; Tue, 15 Dec 2020 20:22:00 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728188AbgLOJVf (ORCPT ); Tue, 15 Dec 2020 04:21:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51160 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728109AbgLOJVc (ORCPT ); Tue, 15 Dec 2020 04:21:32 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E59D3C0617B0 for ; Tue, 15 Dec 2020 01:20:51 -0800 (PST) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kp6Vd-0007FP-Ny; Tue, 15 Dec 2020 10:20:41 +0100 Received: from ukl by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1kp6Vb-00020G-W6; Tue, 15 Dec 2020 10:20:39 +0100 From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= To: Bartlomiej Zolnierkiewicz , Jean Delvare , Guenter Roeck Cc: Thierry Reding , Lee Jones , linux-hwmon@vger.kernel.org, linux-pwm@vger.kernel.org, kernel@pengutronix.de Subject: [PATCH 1/2] hwmon: pwm-fan: Ensure that calculation doesn't discard big period values Date: Tue, 15 Dec 2020 10:20:30 +0100 Message-Id: <20201215092031.152243-1-u.kleine-koenig@pengutronix.de> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-pwm@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org With MAX_PWM being defined to 255 the code unsigned long period; ... period = ctx->pwm->args.period; state.duty_cycle = DIV_ROUND_UP(pwm * (period - 1), MAX_PWM); calculates a too small value for duty_cycle if the configured period is big (either by discarding the 64 bit value ctx->pwm->args.period or by overflowing the multiplication). As this results in a too slow fan and so maybe an overheating machine better be safe than sorry and error out in .probe. Signed-off-by: Uwe Kleine-König --- drivers/hwmon/pwm-fan.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) base-commit: 2c85ebc57b3e1817b6ce1a6b703928e113a90442 diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c index 1f63807c0399..ec171f2b684a 100644 --- a/drivers/hwmon/pwm-fan.c +++ b/drivers/hwmon/pwm-fan.c @@ -324,8 +324,18 @@ static int pwm_fan_probe(struct platform_device *pdev) ctx->pwm_value = MAX_PWM; - /* Set duty cycle to maximum allowed and enable PWM output */ pwm_init_state(ctx->pwm, &state); + /* + * __set_pwm assumes that MAX_PWM * (period - 1) fits into an unsigned + * long. Check this here to prevent the fan running at a too low + * frequency. + */ + if (state.period > ULONG_MAX / MAX_PWM + 1) { + dev_err(dev, "Configured period too big\n"); + return -EINVAL; + } + + /* Set duty cycle to maximum allowed and enable PWM output */ state.duty_cycle = ctx->pwm->args.period - 1; state.enabled = true;