Re: [PATCH] PM / devfreq: Rework freq_table to be local to devfreq struct

[Christian Marangi <ansuelsmth@gmail.com>]

On Fri, Jul 01, 2022 at 10:01:52AM +0200, Marek Szyprowski wrote:
> Hi All,
> 
> On 20.06.2022 00:03, Christian Marangi wrote:
> > On a devfreq PROBE_DEFER, the freq_table in the driver profile struct,
> > is never reset and may be leaved in an undefined state.
> >
> > This comes from the fact that we store the freq_table in the driver
> > profile struct that is commonly defined as static and not reset on
> > PROBE_DEFER.
> > We currently skip the reinit of the freq_table if we found
> > it's already defined since a driver may declare his own freq_table.
> >
> > This logic is flawed in the case devfreq core generate a freq_table, set
> > it in the profile struct and then PROBE_DEFER, freeing the freq_table.
> > In this case devfreq will found a NOT NULL freq_table that has been
> > freed, skip the freq_table generation and probe the driver based on the
> > wrong table.
> >
> > To fix this and correctly handle PROBE_DEFER, use a local freq_table and
> > max_state in the devfreq struct and never modify the freq_table present
> > in the profile struct if it does provide it.
> >
> > Fixes: 0ec09ac2cebe ("PM / devfreq: Set the freq_table of devfreq device")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> > ---
> 
> This patch landed in linux next-20220630 as commit b5d281f6c16d ("PM / 
> devfreq: Rework freq_table to be local to devfreq struct"). 
> Unfortunately it causes the following regression on my Exynos based test 
> systems:
> 
> 8<--- cut here ---
> Unable to handle kernel NULL pointer dereference at virtual address 00000000
> [00000000] *pgd=00000000
> Internal error: Oops: 5 [#1] PREEMPT SMP ARM
> Modules linked in:
> CPU: 3 PID: 49 Comm: kworker/u8:3 Not tainted 5.19.0-rc4-next-20220630 #5312
> Hardware name: Samsung Exynos (Flattened Device Tree)
> Workqueue: events_unbound deferred_probe_work_func
> PC is at exynos_bus_probe+0x604/0x684
> LR is at device_add+0x14c/0x908
> pc : [<c090aef4>]    lr : [<c06cf77c>]    psr: 80000053
> ...
> Process kworker/u8:3 (pid: 49, stack limit = 0x(ptrval))
> Stack: (0xf0a15d30 to 0xf0a16000)
> ...
>   exynos_bus_probe from platform_probe+0x5c/0xb8
>   platform_probe from really_probe+0xe0/0x414
>   really_probe from __driver_probe_device+0xa0/0x208
>   __driver_probe_device from driver_probe_device+0x30/0xc0
>   driver_probe_device from __device_attach_driver+0xa4/0x11c
>   __device_attach_driver from bus_for_each_drv+0x7c/0xc0
>   bus_for_each_drv from __device_attach+0xac/0x20c
>   __device_attach from bus_probe_device+0x88/0x90
>   bus_probe_device from deferred_probe_work_func+0x98/0xe0
>   deferred_probe_work_func from process_one_work+0x288/0x774
>   process_one_work from worker_thread+0x44/0x504
>   worker_thread from kthread+0xf4/0x128
>   kthread from ret_from_fork+0x14/0x2c
> Exception stack(0xf0a15fb0 to 0xf0a15ff8)
> ...
> ---[ end trace 0000000000000000 ]---
> 
> This issue is caused by bus->devfreq->profile->freq_table being NULL here:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/devfreq/exynos-bus.c?h=next-20220630#n451
> 
>

I just checked this and the bug is caused by a simple pr_info...

Can you test the following patch just to make sure?

diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
index b5615e667e31..79725bbb4bb0 100644
--- a/drivers/devfreq/exynos-bus.c
+++ b/drivers/devfreq/exynos-bus.c
@@ -447,9 +447,9 @@ static int exynos_bus_probe(struct platform_device *pdev)
                }
        }

-       max_state = bus->devfreq->profile->max_state;
-       min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
-       max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
+       max_state = bus->devfreq->max_state;
+       min_freq = (bus->devfreq->freq_table[0] / 1000);
+       max_freq = (bus->devfreq->freq_table[max_state - 1] / 1000);
        pr_info("exynos-bus: new bus device registered: %s (%6ld KHz ~ %6ld KHz)\n",
                        dev_name(dev), min_freq, max_freq);
 

> >   drivers/devfreq/devfreq.c          | 71 ++++++++++++++----------------
> >   drivers/devfreq/governor_passive.c | 14 +++---
> >   include/linux/devfreq.h            |  5 +++
> >   3 files changed, 46 insertions(+), 44 deletions(-)
> >
> > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > index 01474daf4548..2e2b3b414d67 100644
> > --- a/drivers/devfreq/devfreq.c
> > +++ b/drivers/devfreq/devfreq.c
> > @@ -123,7 +123,7 @@ void devfreq_get_freq_range(struct devfreq *devfreq,
> >   			    unsigned long *min_freq,
> >   			    unsigned long *max_freq)
> >   {
> > -	unsigned long *freq_table = devfreq->profile->freq_table;
> > +	unsigned long *freq_table = devfreq->freq_table;
> >   	s32 qos_min_freq, qos_max_freq;
> >   
> >   	lockdep_assert_held(&devfreq->lock);
> > @@ -133,11 +133,11 @@ void devfreq_get_freq_range(struct devfreq *devfreq,
> >   	 * The devfreq drivers can initialize this in either ascending or
> >   	 * descending order and devfreq core supports both.
> >   	 */
> > -	if (freq_table[0] < freq_table[devfreq->profile->max_state - 1]) {
> > +	if (freq_table[0] < freq_table[devfreq->max_state - 1]) {
> >   		*min_freq = freq_table[0];
> > -		*max_freq = freq_table[devfreq->profile->max_state - 1];
> > +		*max_freq = freq_table[devfreq->max_state - 1];
> >   	} else {
> > -		*min_freq = freq_table[devfreq->profile->max_state - 1];
> > +		*min_freq = freq_table[devfreq->max_state - 1];
> >   		*max_freq = freq_table[0];
> >   	}
> >   
> > @@ -169,8 +169,8 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
> >   {
> >   	int lev;
> >   
> > -	for (lev = 0; lev < devfreq->profile->max_state; lev++)
> > -		if (freq == devfreq->profile->freq_table[lev])
> > +	for (lev = 0; lev < devfreq->max_state; lev++)
> > +		if (freq == devfreq->freq_table[lev])
> >   			return lev;
> >   
> >   	return -EINVAL;
> > @@ -178,7 +178,6 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
> >   
> >   static int set_freq_table(struct devfreq *devfreq)
> >   {
> > -	struct devfreq_dev_profile *profile = devfreq->profile;
> >   	struct dev_pm_opp *opp;
> >   	unsigned long freq;
> >   	int i, count;
> > @@ -188,25 +187,22 @@ static int set_freq_table(struct devfreq *devfreq)
> >   	if (count <= 0)
> >   		return -EINVAL;
> >   
> > -	profile->max_state = count;
> > -	profile->freq_table = devm_kcalloc(devfreq->dev.parent,
> > -					profile->max_state,
> > -					sizeof(*profile->freq_table),
> > -					GFP_KERNEL);
> > -	if (!profile->freq_table) {
> > -		profile->max_state = 0;
> > +	devfreq->max_state = count;
> > +	devfreq->freq_table = devm_kcalloc(devfreq->dev.parent,
> > +					   devfreq->max_state,
> > +					   sizeof(*devfreq->freq_table),
> > +					   GFP_KERNEL);
> > +	if (!devfreq->freq_table)
> >   		return -ENOMEM;
> > -	}
> >   
> > -	for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
> > +	for (i = 0, freq = 0; i < devfreq->max_state; i++, freq++) {
> >   		opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
> >   		if (IS_ERR(opp)) {
> > -			devm_kfree(devfreq->dev.parent, profile->freq_table);
> > -			profile->max_state = 0;
> > +			devm_kfree(devfreq->dev.parent, devfreq->freq_table);
> >   			return PTR_ERR(opp);
> >   		}
> >   		dev_pm_opp_put(opp);
> > -		profile->freq_table[i] = freq;
> > +		devfreq->freq_table[i] = freq;
> >   	}
> >   
> >   	return 0;
> > @@ -246,7 +242,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
> >   
> >   	if (lev != prev_lev) {
> >   		devfreq->stats.trans_table[
> > -			(prev_lev * devfreq->profile->max_state) + lev]++;
> > +			(prev_lev * devfreq->max_state) + lev]++;
> >   		devfreq->stats.total_trans++;
> >   	}
> >   
> > @@ -835,6 +831,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
> >   		if (err < 0)
> >   			goto err_dev;
> >   		mutex_lock(&devfreq->lock);
> > +	} else {
> > +		devfreq->freq_table = devfreq->profile->freq_table;
> > +		devfreq->max_state = devfreq->profile->max_state;
> >   	}
> >   
> >   	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
> > @@ -870,8 +869,8 @@ struct devfreq *devfreq_add_device(struct device *dev,
> >   
> >   	devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
> >   			array3_size(sizeof(unsigned int),
> > -				    devfreq->profile->max_state,
> > -				    devfreq->profile->max_state),
> > +				    devfreq->max_state,
> > +				    devfreq->max_state),
> >   			GFP_KERNEL);
> >   	if (!devfreq->stats.trans_table) {
> >   		mutex_unlock(&devfreq->lock);
> > @@ -880,7 +879,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
> >   	}
> >   
> >   	devfreq->stats.time_in_state = devm_kcalloc(&devfreq->dev,
> > -			devfreq->profile->max_state,
> > +			devfreq->max_state,
> >   			sizeof(*devfreq->stats.time_in_state),
> >   			GFP_KERNEL);
> >   	if (!devfreq->stats.time_in_state) {
> > @@ -1665,9 +1664,9 @@ static ssize_t available_frequencies_show(struct device *d,
> >   
> >   	mutex_lock(&df->lock);
> >   
> > -	for (i = 0; i < df->profile->max_state; i++)
> > +	for (i = 0; i < df->max_state; i++)
> >   		count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
> > -				"%lu ", df->profile->freq_table[i]);
> > +				"%lu ", df->freq_table[i]);
> >   
> >   	mutex_unlock(&df->lock);
> >   	/* Truncate the trailing space */
> > @@ -1690,7 +1689,7 @@ static ssize_t trans_stat_show(struct device *dev,
> >   
> >   	if (!df->profile)
> >   		return -EINVAL;
> > -	max_state = df->profile->max_state;
> > +	max_state = df->max_state;
> >   
> >   	if (max_state == 0)
> >   		return sprintf(buf, "Not Supported.\n");
> > @@ -1707,19 +1706,17 @@ static ssize_t trans_stat_show(struct device *dev,
> >   	len += sprintf(buf + len, "           :");
> >   	for (i = 0; i < max_state; i++)
> >   		len += sprintf(buf + len, "%10lu",
> > -				df->profile->freq_table[i]);
> > +				df->freq_table[i]);
> >   
> >   	len += sprintf(buf + len, "   time(ms)\n");
> >   
> >   	for (i = 0; i < max_state; i++) {
> > -		if (df->profile->freq_table[i]
> > -					== df->previous_freq) {
> > +		if (df->freq_table[i] == df->previous_freq)
> >   			len += sprintf(buf + len, "*");
> > -		} else {
> > +		else
> >   			len += sprintf(buf + len, " ");
> > -		}
> > -		len += sprintf(buf + len, "%10lu:",
> > -				df->profile->freq_table[i]);
> > +
> > +		len += sprintf(buf + len, "%10lu:", df->freq_table[i]);
> >   		for (j = 0; j < max_state; j++)
> >   			len += sprintf(buf + len, "%10u",
> >   				df->stats.trans_table[(i * max_state) + j]);
> > @@ -1743,7 +1740,7 @@ static ssize_t trans_stat_store(struct device *dev,
> >   	if (!df->profile)
> >   		return -EINVAL;
> >   
> > -	if (df->profile->max_state == 0)
> > +	if (df->max_state == 0)
> >   		return count;
> >   
> >   	err = kstrtoint(buf, 10, &value);
> > @@ -1751,11 +1748,11 @@ static ssize_t trans_stat_store(struct device *dev,
> >   		return -EINVAL;
> >   
> >   	mutex_lock(&df->lock);
> > -	memset(df->stats.time_in_state, 0, (df->profile->max_state *
> > +	memset(df->stats.time_in_state, 0, (df->max_state *
> >   					sizeof(*df->stats.time_in_state)));
> >   	memset(df->stats.trans_table, 0, array3_size(sizeof(unsigned int),
> > -					df->profile->max_state,
> > -					df->profile->max_state));
> > +					df->max_state,
> > +					df->max_state));
> >   	df->stats.total_trans = 0;
> >   	df->stats.last_update = get_jiffies_64();
> >   	mutex_unlock(&df->lock);
> > diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> > index 72c67979ebe1..ce24a262aa16 100644
> > --- a/drivers/devfreq/governor_passive.c
> > +++ b/drivers/devfreq/governor_passive.c
> > @@ -131,18 +131,18 @@ static int get_target_freq_with_devfreq(struct devfreq *devfreq,
> >   		goto out;
> >   
> >   	/* Use interpolation if required opps is not available */
> > -	for (i = 0; i < parent_devfreq->profile->max_state; i++)
> > -		if (parent_devfreq->profile->freq_table[i] == *freq)
> > +	for (i = 0; i < parent_devfreq->max_state; i++)
> > +		if (parent_devfreq->freq_table[i] == *freq)
> >   			break;
> >   
> > -	if (i == parent_devfreq->profile->max_state)
> > +	if (i == parent_devfreq->max_state)
> >   		return -EINVAL;
> >   
> > -	if (i < devfreq->profile->max_state) {
> > -		child_freq = devfreq->profile->freq_table[i];
> > +	if (i < devfreq->max_state) {
> > +		child_freq = devfreq->freq_table[i];
> >   	} else {
> > -		count = devfreq->profile->max_state;
> > -		child_freq = devfreq->profile->freq_table[count - 1];
> > +		count = devfreq->max_state;
> > +		child_freq = devfreq->freq_table[count - 1];
> >   	}
> >   
> >   out:
> > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> > index dc10bee75a72..34aab4dd336c 100644
> > --- a/include/linux/devfreq.h
> > +++ b/include/linux/devfreq.h
> > @@ -148,6 +148,8 @@ struct devfreq_stats {
> >    *		reevaluate operable frequencies. Devfreq users may use
> >    *		devfreq.nb to the corresponding register notifier call chain.
> >    * @work:	delayed work for load monitoring.
> > + * @freq_table:		current frequency table used by the devfreq driver.
> > + * @max_state:		count of entry present in the frequency table.
> >    * @previous_freq:	previously configured frequency value.
> >    * @last_status:	devfreq user device info, performance statistics
> >    * @data:	Private data of the governor. The devfreq framework does not
> > @@ -185,6 +187,9 @@ struct devfreq {
> >   	struct notifier_block nb;
> >   	struct delayed_work work;
> >   
> > +	unsigned long *freq_table;
> > +	unsigned int max_state;
> > +
> >   	unsigned long previous_freq;
> >   	struct devfreq_dev_status last_status;
> >   
> 
> Best regards
> -- 
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
> 

-- 
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