Messages in this thread | | | From | D Scott Phillips <> | Subject | Re: [PATCH] hwmon: (xgene) restrict power measurements to admin by default | Date | Fri, 03 Jun 2022 09:11:01 -0700 |
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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
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