linux-kernel - [RFC PATCH 2/2] hwmon: (pmbus/ucd9000) Throttle SMBus transfers to avoid poor behaviour

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200914122811.3295678-3-andrew@aj.id.au>
Date:   Mon, 14 Sep 2020 21:58:11 +0930
From:   Andrew Jeffery <andrew@...id.au>
To:     linux-hwmon@...r.kernel.org, linux-i2c@...r.kernel.org
Cc:     linux@...ck-us.net, jdelvare@...e.com, wsa@...nel.org,
        joel@....id.au, linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/2] hwmon: (pmbus/ucd9000) Throttle SMBus transfers to avoid poor behaviour

Short turn-around times between transfers to e.g. the UCD90320 can lead
to problematic behaviour, including excessive clock stretching, bus
lockups and potential corruption of the device's volatile state.

Introduce transfer throttling for the device with a minimum access
delay of 1ms.

Signed-off-by: Andrew Jeffery <andrew@...id.au>
---
 drivers/hwmon/pmbus/ucd9000.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
index 81f4c4f166cd..a0b97d035326 100644
--- a/drivers/hwmon/pmbus/ucd9000.c
+++ b/drivers/hwmon/pmbus/ucd9000.c
@@ -9,6 +9,7 @@
 #include <linux/debugfs.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/moduleparam.h>
 #include <linux/of_device.h>
 #include <linux/init.h>
 #include <linux/err.h>
@@ -18,6 +19,9 @@
 #include <linux/gpio/driver.h>
 #include "pmbus.h"
 
+static unsigned long smbus_delay_us = 1000;
+module_param(smbus_delay_us, ulong, 0664);
+
 enum chips { ucd9000, ucd90120, ucd90124, ucd90160, ucd90320, ucd9090,
 	     ucd90910 };
 
@@ -502,6 +506,8 @@ static int ucd9000_probe(struct i2c_client *client,
 				     I2C_FUNC_SMBUS_BLOCK_DATA))
 		return -ENODEV;
 
+	i2c_smbus_throttle_client(client, smbus_delay_us);
+
 	ret = i2c_smbus_read_block_data(client, UCD9000_DEVICE_ID,
 					block_buffer);
 	if (ret < 0) {
-- 
2.25.1