From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 03D452E542B; Tue, 8 Jul 2025 16:24:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751991881; cv=none; b=dlXZNduohNYYQITj2wIvFAXHBF/lJ3qXyrV7daFLzXyxgIrUUvr/UQQPtJ9ebjZmGMA48EXRqaa2p/wpWo9cheUcW4z9gwe6dXzAGEIeEmS+yF0TFgIQzTFnVOcYn0T+koHxegziFny/yWsDO3ku+7Je+t45XQrI9Q1P//dUKJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751991881; c=relaxed/simple; bh=lQKESBdjjKN7fkwxihAXumKjCFMWiWRBPufD2MyYnIc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=SQ6lqB5bfsmtPFVmQt79tbeEpt5zBGZwXdN902KCDKfz98EvjhMMU8l1M/n+hYXHcyMp+s86jxxrvB6e+lW6pweIqcB80NGm685rYX6v1d0iestny/8U5JCZBndkszmKpMOvkG/lHwo+I9cww74qqrOFBAuKiTWhmTvPQgYCxn4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Tf0vHjZn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Tf0vHjZn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8433CC4CEED; Tue, 8 Jul 2025 16:24:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1751991880; bh=lQKESBdjjKN7fkwxihAXumKjCFMWiWRBPufD2MyYnIc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tf0vHjZnTZGp2V70RO1OFPnR8CZ54hYdX0DwypaaPZYGqxwaI9Pd1zeSZrcSWVQBi o5n7SXRqpYtsXWTmgus+UpumH2pOS+sOafV1PwhnRdEwf3INRi0HcLdKQWzk4paQbe jI52mIhKIFuv3gU9OzB364bp7wPtWhLXEHAXw2ik= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Mateusz=20Jo=C5=84czyk?= , Sebastian Andrzej Siewior , Chris Bainbridge , Alexandre Belloni Subject: [PATCH 6.12 003/232] rtc: cmos: use spin_lock_irqsave in cmos_interrupt Date: Tue, 8 Jul 2025 18:19:59 +0200 Message-ID: <20250708162241.521214934@linuxfoundation.org> X-Mailer: git-send-email 2.50.0 In-Reply-To: <20250708162241.426806072@linuxfoundation.org> References: <20250708162241.426806072@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Mateusz Jończyk commit 00a39d8652ff9088de07a6fe6e9e1893452fe0dd upstream. cmos_interrupt() can be called in a non-interrupt context, such as in an ACPI event handler (which runs in an interrupt thread). Therefore, usage of spin_lock(&rtc_lock) is insecure. Use spin_lock_irqsave() / spin_unlock_irqrestore() instead. Before a misguided commit 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ") the cmos_interrupt() function used spin_lock_irqsave(). That commit changed it to spin_lock() and broke locking, which was partially fixed in commit 13be2efc390a ("rtc: cmos: Disable irq around direct invocation of cmos_interrupt()") That second commit did not take account of the ACPI fixed event handler pathway, however. It introduced local_irq_disable() workarounds in cmos_check_wkalrm(), which can cause problems on PREEMPT_RT kernels and are now unnecessary. Add an explicit comment so that this change will not be reverted by mistake. Cc: stable@vger.kernel.org Fixes: 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ") Signed-off-by: Mateusz Jończyk Reviewed-by: Sebastian Andrzej Siewior Tested-by: Chris Bainbridge Reported-by: Chris Bainbridge Closes: https://lore.kernel.org/all/aDtJ92foPUYmGheF@debian.local/ Link: https://lore.kernel.org/r/20250607210608.14835-1-mat.jonczyk@o2.pl Signed-off-by: Alexandre Belloni Signed-off-by: Greg Kroah-Hartman --- drivers/rtc/rtc-cmos.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) --- a/drivers/rtc/rtc-cmos.c +++ b/drivers/rtc/rtc-cmos.c @@ -697,8 +697,12 @@ static irqreturn_t cmos_interrupt(int ir { u8 irqstat; u8 rtc_control; + unsigned long flags; - spin_lock(&rtc_lock); + /* We cannot use spin_lock() here, as cmos_interrupt() is also called + * in a non-irq context. + */ + spin_lock_irqsave(&rtc_lock, flags); /* When the HPET interrupt handler calls us, the interrupt * status is passed as arg1 instead of the irq number. But @@ -732,7 +736,7 @@ static irqreturn_t cmos_interrupt(int ir hpet_mask_rtc_irq_bit(RTC_AIE); CMOS_READ(RTC_INTR_FLAGS); } - spin_unlock(&rtc_lock); + spin_unlock_irqrestore(&rtc_lock, flags); if (is_intr(irqstat)) { rtc_update_irq(p, 1, irqstat); @@ -1300,9 +1304,7 @@ static void cmos_check_wkalrm(struct dev * ACK the rtc irq here */ if (t_now >= cmos->alarm_expires && cmos_use_acpi_alarm()) { - local_irq_disable(); cmos_interrupt(0, (void *)cmos->rtc); - local_irq_enable(); return; }