From: Guenter Roeck <linux@roeck-us.net>
To: "Chatradhi, Naveen Krishna" <NaveenKrishna.Chatradhi@amd.com>
Cc: Salvatore Bonaccorso <carnil@debian.org>,
"linux-hwmon@vger.kernel.org" <linux-hwmon@vger.kernel.org>,
"naveenkrishna.ch@gmail.com" <naveenkrishna.ch@gmail.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] hwmon: amd_energy: modify the visibility of the counters
Date: Sun, 22 Nov 2020 05:30:11 -0800 [thread overview]
Message-ID: <20201122133011.GA48943@roeck-us.net> (raw)
In-Reply-To: <DM6PR12MB438866557FEE8F42C0F6AF26E8FD0@DM6PR12MB4388.namprd12.prod.outlook.com>
On Sun, Nov 22, 2020 at 06:56:24AM +0000, Chatradhi, Naveen Krishna wrote:
> [AMD Official Use Only - Approved for External Use]
>
> Hi Guenter, Salvatore
>
> > This is very unusual, and may mess up the "sensors" command.
> > What problem is this trying to solve ?
> Guenter, sorry for the delayed response.
> This fix is required to address the possible side channel attack reported in CVE-2020-12912.
>
[ ... ]
>
> >> ?
> Yes, Salvatore, thanks for bringing the links.
>
A much better fix would have been to cache RAPL data for a short period
of time. To avoid any possibility of attacks, maybe add some random
interval. Something like this:
In accumulate_delta():
accums->next_update = jiffies + HZ / 2 + get_random_int % HZ;
In amd_energy_read():
accum = &data->accums[channel];
if (time_after(accum->next_update))
accumulate_delta(data, channel, cpu, reg);
*val = div64_ul(accum->energy_ctr * 1000000UL, BIT(data->energy_units));
and drop amd_add_delta().
Guenter
next prev parent reply other threads:[~2020-11-22 13:42 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-12 17:21 [PATCH] hwmon: amd_energy: modify the visibility of the counters Naveen Krishna Chatradhi
2020-11-12 17:24 ` Guenter Roeck
2020-11-13 13:58 ` Salvatore Bonaccorso
2020-11-13 14:47 ` Guenter Roeck
2020-11-22 6:56 ` Chatradhi, Naveen Krishna
2020-11-22 13:30 ` Guenter Roeck [this message]
2020-11-22 16:42 ` Chatradhi, Naveen Krishna
2020-11-22 18:09 ` Guenter Roeck
-- strict thread matches above, loose matches on Subject: below --
2020-11-09 9:07 Naveen Krishna Chatradhi
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