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SubjectRe: [BUG] dev_pm_opp refcount issue on Arm Juno r0
On 20-12-18, 15:27, Valentin Schneider wrote:
> Hi,
>
> While running some hotplug torture test [1] on my Juno r0 I came across
> the follow splat:
>
> [ 716.561862] ------------[ cut here ]------------
> [ 716.566451] refcount_t: underflow; use-after-free.
> [ 716.571240] WARNING: CPU: 2 PID: 18 at lib/refcount.c:280 refcount_dec_not_one+0x9c/0xc0
> [ 716.579246] Modules linked in:
> [ 716.582269] CPU: 2 PID: 18 Comm: cpuhp/2 Not tainted 4.20.0-rc7 #39
> [ 716.588469] Hardware name: ARM Juno development board (r0) (DT)
> [ 716.594326] pstate: 40000005 (nZcv daif -PAN -UAO)
> [ 716.599065] pc : refcount_dec_not_one+0x9c/0xc0
> [ 716.603546] lr : refcount_dec_not_one+0x9c/0xc0
> [ 716.608024] sp : ffff00000a063c70
> [ 716.611299] x29: ffff00000a063c70 x28: 0000000000000000
> [ 716.616555] x27: 0000000000000000 x26: 0000000000000002
> [ 716.621810] x25: ffff000009169000 x24: ffff000008f8e1b0
> [ 716.627065] x23: ffff000008ce0920 x22: 00000000ffffffff
> [ 716.632319] x21: ffff000009169000 x20: ffff8009762a2664
> [ 716.637574] x19: ffff000009294a90 x18: 0000000000000400
> [ 716.642828] x17: 0000000000000000 x16: 0000000000000000
> [ 716.648082] x15: 0000000000000000 x14: 0000000000000400
> [ 716.653336] x13: 000000000000023f x12: 0000000000043705
> [ 716.658590] x11: 0000000000000108 x10: 0000000000000960
> [ 716.663844] x9 : ffff00000a063970 x8 : ffff800976943ec0
> [ 716.669098] x7 : 0000000000000000 x6 : ffff80097ff720b8
> [ 716.674353] x5 : ffff80097ff720b8 x4 : 0000000000000000
> [ 716.679607] x3 : ffff80097ff78e68 x2 : ffff80097ff720b8
> [ 716.684861] x1 : 6374e2a7925c1100 x0 : 0000000000000000
> [ 716.690115] Call trace:
> [ 716.692532] refcount_dec_not_one+0x9c/0xc0
> [ 716.696669] refcount_dec_and_mutex_lock+0x18/0x70
> [ 716.701409] _put_opp_list_kref+0x28/0x50
> [ 716.705373] _dev_pm_opp_find_and_remove_table+0x24/0x88
> [ 716.710628] _dev_pm_opp_cpumask_remove_table+0x50/0xa0
> [ 716.715796] dev_pm_opp_cpumask_remove_table+0x10/0x18
> [ 716.720879] scpi_cpufreq_exit+0x40/0x50
> [ 716.724758] cpufreq_offline+0x108/0x1e0
> [ 716.728637] cpuhp_cpufreq_offline+0xc/0x18

This probably happened due to some of recent OPP core changes and I missed
updating this platform (I updated mvebu though). The problem is completely
different from what you logs show :)

Please try the below patch.

@Sudeep: Please help review it as well.

--
viresh

-------------------------8<-------------------------

From f3913738618031e9d71ebf64461cee22909e6e20 Mon Sep 17 00:00:00 2001
Message-Id: <f3913738618031e9d71ebf64461cee22909e6e20.1546498940.git.viresh.kumar@linaro.org>
From: Viresh Kumar <viresh.kumar@linaro.org>
Date: Thu, 3 Jan 2019 12:28:26 +0530
Subject: [PATCH] cpufreq: scpi: Fix freeing of OPPs

Since the commit 2a4eb7358aba ("OPP: Don't remove dynamic OPPs from
_dev_pm_opp_remove_table()"), dynamically created OPP aren't
automatically removed anymore by dev_pm_opp_cpumask_remove_table().

The OPPs for scpi cpufreq driver aren't getting freed currently, fix
that by adding a new callback scpi_ops->remove_device_opps() which will
remove those OPPs.

Cc: 4.20 <stable@vger.kernel.org> # v4.20
Reported-by: Valentin Schneider <valentin.schneider@arm.com>
Fixes: 2a4eb7358aba ("OPP: Don't remove dynamic OPPs from _dev_pm_opp_remove_table()")
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
drivers/cpufreq/scpi-cpufreq.c | 4 ++--
drivers/firmware/arm_scpi.c | 15 +++++++++++++++
include/linux/scpi_protocol.h | 1 +
3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/scpi-cpufreq.c b/drivers/cpufreq/scpi-cpufreq.c
index 87a98ec77773..1bfd168de0b2 100644
--- a/drivers/cpufreq/scpi-cpufreq.c
+++ b/drivers/cpufreq/scpi-cpufreq.c
@@ -177,7 +177,7 @@ static int scpi_cpufreq_init(struct cpufreq_policy *policy)
out_free_priv:
kfree(priv);
out_free_opp:
- dev_pm_opp_cpumask_remove_table(policy->cpus);
+ scpi_ops->remove_device_opps(cpu_dev);

return ret;
}
@@ -190,7 +190,7 @@ static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
clk_put(priv->clk);
dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
kfree(priv);
- dev_pm_opp_cpumask_remove_table(policy->related_cpus);
+ scpi_ops->remove_device_opps(priv->cpu_dev);

return 0;
}
diff --git a/drivers/firmware/arm_scpi.c b/drivers/firmware/arm_scpi.c
index c7d06a36b23a..963f2ffbd820 100644
--- a/drivers/firmware/arm_scpi.c
+++ b/drivers/firmware/arm_scpi.c
@@ -716,6 +716,20 @@ static int scpi_dvfs_add_opps_to_device(struct device *dev)
return 0;
}

+static void scpi_dvfs_remove_device_opps(struct device *dev)
+{
+ int idx;
+ struct scpi_opp *opp;
+ struct scpi_dvfs_info *info = scpi_dvfs_info(dev);
+
+ /* We already added OPPs successfully, this data can't be invalid */
+ if (WARN_ON(IS_ERR(info) || !info->opps))
+ return;
+
+ for (opp = info->opps, idx = 0; idx < info->count; idx++, opp++)
+ dev_pm_opp_remove(dev, opp->freq);
+}
+
static int scpi_sensor_get_capability(u16 *sensors)
{
__le16 cap;
@@ -799,6 +813,7 @@ static struct scpi_ops scpi_ops = {
.device_domain_id = scpi_dev_domain_id,
.get_transition_latency = scpi_dvfs_get_transition_latency,
.add_opps_to_device = scpi_dvfs_add_opps_to_device,
+ .remove_device_opps = scpi_dvfs_remove_device_opps,
.sensor_get_capability = scpi_sensor_get_capability,
.sensor_get_info = scpi_sensor_get_info,
.sensor_get_value = scpi_sensor_get_value,
diff --git a/include/linux/scpi_protocol.h b/include/linux/scpi_protocol.h
index 327d65663dbf..d020d517ecaa 100644
--- a/include/linux/scpi_protocol.h
+++ b/include/linux/scpi_protocol.h
@@ -70,6 +70,7 @@ struct scpi_ops {
int (*device_domain_id)(struct device *);
int (*get_transition_latency)(struct device *);
int (*add_opps_to_device)(struct device *);
+ void (*remove_device_opps)(struct device *);
int (*sensor_get_capability)(u16 *sensors);
int (*sensor_get_info)(u16 sensor_id, struct scpi_sensor_info *);
int (*sensor_get_value)(u16, u64 *);
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