linux-kernel - [PATCH 4.18 075/168] firmware: arm_scmi: fix divide by zero when sustained_perf

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Date:   Mon,  8 Oct 2018 20:30:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ionela Voinescu <ionela.voinescu@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Olof Johansson <olof@...om.net>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.18 075/168] firmware: arm_scmi: fix divide by zero when sustained_perf_level is zero

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sudeep Holla <sudeep.holla@....com>

[ Upstream commit 96d529bac562574600eda85726fcfa3eef6dde8e ]

Firmware can provide zero as values for sustained performance level and
corresponding sustained frequency in kHz in order to hide the actual
frequencies and provide only abstract values. It may endup with divide
by zero scenario resulting in kernel panic.

Let's set the multiplication factor to one if either one or both of them
(sustained_perf_level and sustained_freq) are set to zero.

Fixes: a9e3fbfaa0ff ("firmware: arm_scmi: add initial support for performance protocol")
Reported-by: Ionela Voinescu <ionela.voinescu@....com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
Signed-off-by: Olof Johansson <olof@...om.net>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/firmware/arm_scmi/perf.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/firmware/arm_scmi/perf.c
+++ b/drivers/firmware/arm_scmi/perf.c
@@ -166,7 +166,13 @@ scmi_perf_domain_attributes_get(const st
 					le32_to_cpu(attr->sustained_freq_khz);
 		dom_info->sustained_perf_level =
 					le32_to_cpu(attr->sustained_perf_level);
-		dom_info->mult_factor =	(dom_info->sustained_freq_khz * 1000) /
+		if (!dom_info->sustained_freq_khz ||
+		    !dom_info->sustained_perf_level)
+			/* CPUFreq converts to kHz, hence default 1000 */
+			dom_info->mult_factor =	1000;
+		else
+			dom_info->mult_factor =
+					(dom_info->sustained_freq_khz * 1000) /
 					dom_info->sustained_perf_level;
 		memcpy(dom_info->name, attr->name, SCMI_MAX_STR_SIZE);
 	}