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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27F35C433F5 for ; Mon, 24 Jan 2022 21:28:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1451078AbiAXVWE (ORCPT ); Mon, 24 Jan 2022 16:22:04 -0500 Received: from dfw.source.kernel.org ([139.178.84.217]:47652 "EHLO dfw.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1442282AbiAXUyL (ORCPT ); Mon, 24 Jan 2022 15:54:11 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4796960B11; Mon, 24 Jan 2022 20:54:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21F93C340E5; Mon, 24 Jan 2022 20:54:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1643057650; bh=MFXndqI8cxiHslc/dNlSaB1r9JTjhtiZBSwFf6F0MWk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RN5XSu4x+4I7lIaV5IqOITU4SiDvbdIq3binhcXMFPTfvsG4iPK5uEcUr4xra2MLE gCwj9JsElybIgnI8IwRJbkfAfYpbY1wAGPSlI+xArmzhF6VWgWK3GXQWBzjiuIshSP C6pMLAEiBmfgClA7S7Kgk2jGAeGgVueJ9Fi/NA6M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= , Nobuhiro Iwamatsu , Alessandro Zummo , Alexandre Belloni Subject: [PATCH 5.16 0034/1039] rtc: cmos: take rtc_lock while reading from CMOS Date: Mon, 24 Jan 2022 19:30:23 +0100 Message-Id: <20220124184126.276033378@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220124184125.121143506@linuxfoundation.org> References: <20220124184125.121143506@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mateusz Jończyk commit 454f47ff464325223129b9b5b8d0b61946ec704d upstream. Reading from the CMOS involves writing to the index register and then reading from the data register. Therefore access to the CMOS has to be serialized with rtc_lock. This invocation of CMOS_READ was not serialized, which could cause trouble when other code is accessing CMOS at the same time. Use spin_lock_irq() like the rest of the function. Nothing in kernel modifies the RTC_DM_BINARY bit, so there could be a separate pair of spin_lock_irq() / spin_unlock_irq() before doing the math. Signed-off-by: Mateusz Jończyk Reviewed-by: Nobuhiro Iwamatsu Cc: Alessandro Zummo Cc: Alexandre Belloni Cc: stable@vger.kernel.org Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20211210200131.153887-2-mat.jonczyk@o2.pl Signed-off-by: Greg Kroah-Hartman --- drivers/rtc/rtc-cmos.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -457,7 +457,10 @@ static int cmos_set_alarm(struct device min = t->time.tm_min; sec = t->time.tm_sec; + spin_lock_irq(&rtc_lock); rtc_control = CMOS_READ(RTC_CONTROL); + spin_unlock_irq(&rtc_lock); + if (!(rtc_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD) { /* Writing 0xff means "don't care" or "match all". */ mon = (mon <= 12) ? bin2bcd(mon) : 0xff;