From: Sudeep Holla <sudeep.holla@arm.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>, linux-acpi@vger.kernel.org
Subject: Re: [bug report] ACPI / processor_idle: Add support for Low Power Idle(LPI) states
Date: Tue, 25 Oct 2016 10:12:11 +0100 [thread overview]
Message-ID: <2a67c6fc-602f-9bce-9dd4-d911789d5c0b@arm.com> (raw)
In-Reply-To: <20161025084352.GA21587@elgon.mountain>
Hi Dan,
I am finding it difficult to understand this bug report. Please help.
On 25/10/16 09:43, Dan Carpenter wrote:
> Hello Sudeep Holla,
>
> The patch a36a7fecfe60: "ACPI / processor_idle: Add support for Low
> Power Idle(LPI) states" from Jul 21, 2016, leads to the following
> static checker warning:
>
> drivers/acpi/processor_idle.c:1261 acpi_processor_setup_lpi_states()
> warn: buffer overflow 'pr->power.lpi_states' 8 <= 9
>
> drivers/acpi/processor_idle.c
> 1250 static int acpi_processor_setup_lpi_states(struct acpi_processor *pr)
> 1251 {
> 1252 int i;
> 1253 struct acpi_lpi_state *lpi;
> 1254 struct cpuidle_state *state;
> 1255 struct cpuidle_driver *drv = &acpi_idle_driver;
> 1256
> 1257 if (!pr->flags.has_lpi)
> 1258 return -EOPNOTSUPP;
> 1259
Currently CPUIDLE_STATE_MAX = 10 and ACPI_PROCESSOR_MAX_POWER = 8
> 1260 for (i = 0; i < pr->power.count && i < CPUIDLE_STATE_MAX; i++) {
>
^^^^^^^^^^^^^^^^^
We have drv->states[10] and pr->power.lpi_states[8] and above check is
to ensure we take the minimum of the 2 so that the logic continues to
work if either of these are changed.
>
> Should this be ACPI_PROCESSOR_MAX_POWER?
No, because we don't want to overflow CPUIDLE_STATE_MAX too in case
that's reduced to say 6. pr->power.count is assured to be <=
ACPI_PROCESSOR_MAX_POWER
>
> 1261 lpi = &pr->power.lpi_states[i];
> ^^^^^^^^^^
> because that's how many elements we have in this array.
>
Yes that's correct but i < CPUIDLE_STATE_MAX is to ensure we don't
overflow drv->states.
Let me know if I am being stupid and not able to understand something here.
--
Regards,
Sudeep
next prev parent reply other threads:[~2016-10-25 9:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-25 8:43 [bug report] ACPI / processor_idle: Add support for Low Power Idle(LPI) states Dan Carpenter
2016-10-25 9:12 ` Sudeep Holla [this message]
2016-10-25 9:23 ` Dan Carpenter
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