lkml.org 
[lkml]   [2022]   [Jun]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH] hwmon: (xgene) restrict power measurements to admin by default
Date
Guenter Roeck <linux@roeck-us.net> writes:

> On 6/3/22 08:21, D Scott Phillips wrote:
>> Access to power information can be used to infer the instructions being run
>> and possibly even data being processed on a cpu[1]. Restrict access to
>> power information to administrator users by default. (Cf. a similar
>> powercap change[2].)
>>
>> [1]: Lipp, Moritz, et al. "PLATYPUS: software-based power side-channel
>> attacks on x86." 2021 IEEE Symposium on Security and Privacy (SP).
>> IEEE, 2021.
>> [2]: commit 949dd0104c49 ("powercap: restrict energy meter to root access")
>>
>> Fixes: ed42cfa881e1 ("hwmon: Add xgene hwmon driver")
>> Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
>> Cc: stable@vger.kernel.org
>> ---
>> drivers/hwmon/xgene-hwmon.c | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/hwmon/xgene-hwmon.c b/drivers/hwmon/xgene-hwmon.c
>> index 5cde837bfd09..6ad1daf2d354 100644
>> --- a/drivers/hwmon/xgene-hwmon.c
>> +++ b/drivers/hwmon/xgene-hwmon.c
>> @@ -397,9 +397,9 @@ static DEVICE_ATTR_RO(temp1_label);
>> static DEVICE_ATTR_RO(temp1_input);
>> static DEVICE_ATTR_RO(temp1_critical_alarm);
>> static DEVICE_ATTR_RO(power1_label);
>> -static DEVICE_ATTR_RO(power1_input);
>> +static DEVICE_ATTR_ADMIN_RO(power1_input);
>> static DEVICE_ATTR_RO(power2_label);
>> -static DEVICE_ATTR_RO(power2_input);
>> +static DEVICE_ATTR_ADMIN_RO(power2_input);
>>
>> static struct attribute *xgene_hwmon_attrs[] = {
>> &dev_attr_temp1_label.attr,
>
>
> NACK. The hwmon ABI expects world read access. Either find a workaround
> by making the measurements less accurate, or drop the driver. Also see
> commit 9049572fb145 ("hwmon: Remove amd_energy driver"), "Attribute access"
> in Documentation/hwmon/sysfs-interface.rst, and [1].

Ah, I see, thanks for pointing that out, I had missed that. I'm not
confident that the randomization approach can provide robustness against
this attack, so I'll follow up with a patch to drop the driver. Cheers,

Scott

\
 
 \ /
  Last update: 2022-06-03 18:12    [W:0.041 / U:1.664 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site