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 <[email protected]>
> Cc: [email protected]
> ---
> 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].
Guenter
---
[1] https://patchwork.kernel.org/project/linux-hwmon/patch/[email protected]/
Guenter Roeck <[email protected]> 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 <[email protected]>
>> Cc: [email protected]
>> ---
>> 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