linux-kernel - Re: [v2 PATCH] powernv-cpuidle: Validate DT property array size

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Message-Id: <6d2873de-ee47-e362-ef1a-6ac11ebee121@linux.vnet.ibm.com>
Date:   Fri, 24 Mar 2017 14:15:25 +0530
From:   Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
To:     "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Michael Neuling <mikey@...ling.org>,
        Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
        "Shreyas B. Prabhu" <shreyasbp@...il.com>,
        Balbir Singh <bsingharora@...il.com>,
        Stewart Smith <stewart@...ux.vnet.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [v2 PATCH] powernv-cpuidle: Validate DT property array size



On 03/15/2017 01:45 PM, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <ego@...ux.vnet.ibm.com>
> 
> The various properties associated with powernv idle states such as
> names, flags, residency-ns, latencies-ns, psscr, psscr-mask are
> exposed in the device-tree as property arrays such the pointwise
> entries in each of these arrays correspond to the properties of the
> same idle state.
> 
> This patch validates that the lengths of the property arrays are the
> same. If there is a mismatch, the patch will ensure that we bail out
> and not expose the platform idle states via cpuidle.
> 
> Signed-off-by: Gautham R. Shenoy <ego@...ux.vnet.ibm.com>
> ---
> v1: https://lkml.org/lkml/2017/2/23/349
> Changes from v1: Print the full property array name in warning message.

Reviewed-by: Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>

> 
>  drivers/cpuidle/cpuidle-powernv.c | 64 +++++++++++++++++++++++++++++++++++++--
>  1 file changed, 61 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index 3705930..a06df51 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -197,11 +197,25 @@ static inline void add_powernv_state(int index, const char *name,
>  	stop_psscr_table[index].mask = psscr_mask;
>  }
> 
> +/*
> + * Returns 0 if prop1_len == prop2_len. Else returns -1
> + */
> +static inline int validate_dt_prop_sizes(const char *prop1, int prop1_len,
> +					 const char *prop2, int prop2_len)
> +{
> +	if (prop1_len == prop2_len)
> +		return 0;
> +
> +	pr_warn("cpuidle-powernv: array sizes don't match for %s and %s\n",
> +		prop1, prop2);
> +	return -1;
> +}
> +
>  static int powernv_add_idle_states(void)
>  {
>  	struct device_node *power_mgt;
>  	int nr_idle_states = 1; /* Snooze */
> -	int dt_idle_states;
> +	int dt_idle_states, count;
>  	u32 latency_ns[CPUIDLE_STATE_MAX];
>  	u32 residency_ns[CPUIDLE_STATE_MAX];
>  	u32 flags[CPUIDLE_STATE_MAX];
> @@ -226,6 +240,21 @@ static int powernv_add_idle_states(void)
>  		goto out;
>  	}
> 
> +	count = of_property_count_u32_elems(power_mgt,
> +					    "ibm,cpu-idle-state-latencies-ns");
> +
> +	if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags", dt_idle_states,
> +				   "ibm,cpu-idle-state-latencies-ns",
> +				   count) != 0)
> +		goto out;
> +
> +	count = of_property_count_strings(power_mgt,
> +					  "ibm,cpu-idle-state-names");
> +	if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags", dt_idle_states,
> +				   "ibm,cpu-idle-state-names",
> +				   count) != 0)
> +		goto out;
> +
>  	/*
>  	 * Since snooze is used as first idle state, max idle states allowed is
>  	 * CPUIDLE_STATE_MAX -1
> @@ -260,6 +289,22 @@ static int powernv_add_idle_states(void)
>  	has_stop_states = (flags[0] &
>  			   (OPAL_PM_STOP_INST_FAST | OPAL_PM_STOP_INST_DEEP));
>  	if (has_stop_states) {
> +		count = of_property_count_u64_elems(power_mgt,
> +						    "ibm,cpu-idle-state-psscr");
> +		if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags",
> +					   dt_idle_states,
> +					   "ibm,cpu-idle-state-psscr",
> +					   count) != 0)
> +			goto out;
> +
> +		count = of_property_count_u64_elems(power_mgt,
> +						    "ibm,cpu-idle-state-psscr-mask");
> +		if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags",
> +					   dt_idle_states,
> +					   "ibm,cpu-idle-state-psscr-mask",
> +					   count) != 0)
> +			goto out;
> +
>  		if (of_property_read_u64_array(power_mgt,
>  		    "ibm,cpu-idle-state-psscr", psscr_val, dt_idle_states)) {
>  			pr_warn("cpuidle-powernv: missing ibm,cpu-idle-state-psscr in DT\n");
> @@ -274,8 +319,21 @@ static int powernv_add_idle_states(void)
>  		}
>  	}
> 
> -	rc = of_property_read_u32_array(power_mgt,
> -		"ibm,cpu-idle-state-residency-ns", residency_ns, dt_idle_states);
> +	count = of_property_count_u32_elems(power_mgt,
> +					    "ibm,cpu-idle-state-residency-ns");
> +
> +	if (count < 0) {
> +		rc = count;
> +	} else if (validate_dt_prop_sizes("ibm,cpu-idle-state-flags",
> +					  dt_idle_states,
> +					  "ibm,cpu-idle-state-residency-ns",
> +					  count) != 0) {
> +		goto out;
> +	} else {
> +		rc = of_property_read_u32_array(power_mgt,
> +						"ibm,cpu-idle-state-residency-ns",
> +						residency_ns, dt_idle_states);
> +	}
> 
>  	for (i = 0; i < dt_idle_states; i++) {
>  		unsigned int exit_latency, target_residency;
>