From: "Pali Rohár" <pali.rohar@gmail.com>
To: "Jean Delvare" <jdelvare@suse.com>,
"Guenter Roeck" <linux@roeck-us.net>,
Mario_Limonciello@dell.com,
"Gabriele Mazzotta" <gabriele.mzt@gmail.com>,
"Michał Kępień" <kernel@kempniu.pl>
Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: dell-smm-hwmon: security problems
Date: Wed, 8 Jun 2016 11:57:22 +0200 [thread overview]
Message-ID: <201606081157.22900@pali> (raw)
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Hello!
Mario wrote me about two I think security problems in dell-smm-hwmon
driver and I would like to ask you, how to fix them.
1) File /proc/i8k (exists only when kernel is compiled with CONFIG_I8K)
exports DMI_PRODUCT_SERIAL and it can be read by ordinary user, without
root permission. Normally DMI_PRODUCT_SERIAL can be read from sysfs file
/sys/class/dmi/id/product_serial but only by root user.
2) Via /proc/i8k ordinary user can set fan speed. This is because how
"restricted" parameter and variable works. Setting fan speed by normal
non-root user can be dangerous, e.g. malicious application under user
"nobody" could take control of fans.
Do you have idea how to fix these problems? Just to note that /proc/i8k
has stable kernel ABI and changing it will break all existing i8k*
applications. But /proc/i8k is there only for old legacy laptops (year
2000).
There is module parameter "restricted" with default value false and
description: "Allow fan control if SYS_ADMIN capability set". Current
code do:
case I8K_SET_FAN:
if (restricted && !capable(CAP_SYS_ADMIN))
return -EPERM;
For me description is a bit ambiguous. What about setting "restricted"
by default to true and updating description to something like this?
"Disallow fan control when SYS_ADMIN capability is not set (default: 1)"
--
Pali Rohár
pali.rohar@gmail.com
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next reply other threads:[~2016-06-08 9:57 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-08 9:57 Pali Rohár [this message]
2016-06-08 13:24 ` dell-smm-hwmon: security problems Guenter Roeck
2016-06-08 13:55 ` Pali Rohár
2016-06-08 17:37 ` Guenter Roeck
2016-06-08 17:54 ` Austin S. Hemmelgarn
2016-06-08 18:10 ` Pali Rohár
2016-06-08 18:10 ` Pali Rohár
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