* [PATCH] hwmon: (xgene) restrict power measurements to admin by default
@ 2022-06-03 15:21 D Scott Phillips
2022-06-03 15:37 ` Guenter Roeck
0 siblings, 1 reply; 3+ messages in thread
From: D Scott Phillips @ 2022-06-03 15:21 UTC (permalink / raw)
To: linux-hwmon
Cc: Jean Delvare, Guenter Roeck, linux-kernel, patches, Darren Hart,
Ilkka Koskinen
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,
--
2.35.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] hwmon: (xgene) restrict power measurements to admin by default
2022-06-03 15:21 [PATCH] hwmon: (xgene) restrict power measurements to admin by default D Scott Phillips
@ 2022-06-03 15:37 ` Guenter Roeck
2022-06-03 16:11 ` D Scott Phillips
0 siblings, 1 reply; 3+ messages in thread
From: Guenter Roeck @ 2022-06-03 15:37 UTC (permalink / raw)
To: D Scott Phillips, linux-hwmon
Cc: Jean Delvare, linux-kernel, patches, Darren Hart, Ilkka Koskinen
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].
Guenter
---
[1] https://patchwork.kernel.org/project/linux-hwmon/patch/20210409174852.4585-2-linux@roeck-us.net/
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] hwmon: (xgene) restrict power measurements to admin by default
2022-06-03 15:37 ` Guenter Roeck
@ 2022-06-03 16:11 ` D Scott Phillips
0 siblings, 0 replies; 3+ messages in thread
From: D Scott Phillips @ 2022-06-03 16:11 UTC (permalink / raw)
To: Guenter Roeck, linux-hwmon
Cc: Jean Delvare, linux-kernel, patches, Darren Hart, Ilkka Koskinen
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
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-06-03 16:11 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2022-06-03 15:21 [PATCH] hwmon: (xgene) restrict power measurements to admin by default D Scott Phillips
2022-06-03 15:37 ` Guenter Roeck
2022-06-03 16:11 ` D Scott Phillips
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