Re: [PATCH] thermal: Fix NULL pointer dereference issue
On 17/11/2020 12:27, Zhang Rui wrote:
> On Tue, 2020-11-17 at 09:57 +0100, Daniel Lezcano wrote:
>> On 17/11/2020 08:18, Zhang Rui wrote:
>>> On Mon, 2020-11-16 at 21:59 +0530, Mukesh Ojha wrote:
Cooling stats variable inside
thermal_cooling_device_stats_update()
can get NULL. We should add a NULL check on stat inside for
sanity.
Signed-off-by: Mukesh Ojha
---
drivers/thermal/thermal_sysfs.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/thermal/thermal_sysfs.c
b/drivers/thermal/thermal_sysfs.c
index a6f371f..f52708f 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -754,6 +754,9 @@ void
thermal_cooling_device_stats_update(struct
thermal_cooling_device *cdev,
{
struct cooling_dev_stats *stats = cdev->stats;
+ if (!stats)
+ return;
+
>>>
>>> May I know in which case stats can be NULL?
>>> The only possibility I can see is that cdev->ops->get_max_state()
>>> fails
>>> in cooling_device_stats_setup(), right?
>>
>> A few lines below, the allocation could fail.
>>
>> stats = kzalloc(var, GFP_KERNEL);
>> if (!stats)
>> return;
>>
>> Some drivers define themselves as a cooling device state to let the
>> userspace to act on their power. The screen brightness is one example
>> with a cdev with 1024 states, the resulting stats table to be
>> allocated
>> is very big and the kzalloc is prone to fail.
>>
> Oh, right.
> As we're not going to fix the cdev, so I think we do need this patch,
> right?
If the allocation fails at this level if initialization there is clearly
something wrong. I'm wondering if it would make sense to report back an
error and make thermal_cooling_device_register to fail.
Having an allocation failing and silently ignore it sounds like not very
robust IMO.
--
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Re: [PATCH] thermal: Fix NULL pointer dereference issue
On Tue, 2020-11-17 at 09:57 +0100, Daniel Lezcano wrote:
> On 17/11/2020 08:18, Zhang Rui wrote:
> > On Mon, 2020-11-16 at 21:59 +0530, Mukesh Ojha wrote:
> > > Cooling stats variable inside
> > > thermal_cooling_device_stats_update()
> > > can get NULL. We should add a NULL check on stat inside for
> > > sanity.
> > >
> > > Signed-off-by: Mukesh Ojha
> > > ---
> > > drivers/thermal/thermal_sysfs.c | 3 +++
> > > 1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/thermal/thermal_sysfs.c
> > > b/drivers/thermal/thermal_sysfs.c
> > > index a6f371f..f52708f 100644
> > > --- a/drivers/thermal/thermal_sysfs.c
> > > +++ b/drivers/thermal/thermal_sysfs.c
> > > @@ -754,6 +754,9 @@ void
> > > thermal_cooling_device_stats_update(struct
> > > thermal_cooling_device *cdev,
> > > {
> > > struct cooling_dev_stats *stats = cdev->stats;
> > >
> > > + if (!stats)
> > > + return;
> > > +
> >
> > May I know in which case stats can be NULL?
> > The only possibility I can see is that cdev->ops->get_max_state()
> > fails
> > in cooling_device_stats_setup(), right?
>
> A few lines below, the allocation could fail.
>
> stats = kzalloc(var, GFP_KERNEL);
> if (!stats)
> return;
>
> Some drivers define themselves as a cooling device state to let the
> userspace to act on their power. The screen brightness is one example
> with a cdev with 1024 states, the resulting stats table to be
> allocated
> is very big and the kzalloc is prone to fail.
>
Oh, right.
As we're not going to fix the cdev, so I think we do need this patch,
right?
thanks,
rui
> > thanks,
> > rui
> >
> > > spin_lock(>lock);
> > >
> > > if (stats->state == new_state)
>
>
Re: [PATCH] thermal: Fix NULL pointer dereference issue
On 17/11/2020 08:18, Zhang Rui wrote:
> On Mon, 2020-11-16 at 21:59 +0530, Mukesh Ojha wrote:
>> Cooling stats variable inside thermal_cooling_device_stats_update()
>> can get NULL. We should add a NULL check on stat inside for sanity.
>>
>> Signed-off-by: Mukesh Ojha
>> ---
>> drivers/thermal/thermal_sysfs.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/thermal/thermal_sysfs.c
>> b/drivers/thermal/thermal_sysfs.c
>> index a6f371f..f52708f 100644
>> --- a/drivers/thermal/thermal_sysfs.c
>> +++ b/drivers/thermal/thermal_sysfs.c
>> @@ -754,6 +754,9 @@ void thermal_cooling_device_stats_update(struct
>> thermal_cooling_device *cdev,
>> {
>> struct cooling_dev_stats *stats = cdev->stats;
>>
>> +if (!stats)
>> +return;
>> +
> May I know in which case stats can be NULL?
> The only possibility I can see is that cdev->ops->get_max_state() fails
> in cooling_device_stats_setup(), right?
A few lines below, the allocation could fail.
stats = kzalloc(var, GFP_KERNEL);
if (!stats)
return;
Some drivers define themselves as a cooling device state to let the
userspace to act on their power. The screen brightness is one example
with a cdev with 1024 states, the resulting stats table to be allocated
is very big and the kzalloc is prone to fail.
> thanks,
> rui
>
>> spin_lock(>lock);
>>
>> if (stats->state == new_state)
>
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Re: [PATCH] thermal: Fix NULL pointer dereference issue
On Mon, 2020-11-16 at 21:59 +0530, Mukesh Ojha wrote:
> Cooling stats variable inside thermal_cooling_device_stats_update()
> can get NULL. We should add a NULL check on stat inside for sanity.
>
> Signed-off-by: Mukesh Ojha
> ---
> drivers/thermal/thermal_sysfs.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/thermal/thermal_sysfs.c
> b/drivers/thermal/thermal_sysfs.c
> index a6f371f..f52708f 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -754,6 +754,9 @@ void thermal_cooling_device_stats_update(struct
> thermal_cooling_device *cdev,
> {
> struct cooling_dev_stats *stats = cdev->stats;
>
> + if (!stats)
> + return;
> +
May I know in which case stats can be NULL?
The only possibility I can see is that cdev->ops->get_max_state() fails
in cooling_device_stats_setup(), right?
thanks,
rui
> spin_lock(>lock);
>
> if (stats->state == new_state)
[PATCH] thermal: Fix NULL pointer dereference issue
Cooling stats variable inside thermal_cooling_device_stats_update()
can get NULL. We should add a NULL check on stat inside for sanity.
Signed-off-by: Mukesh Ojha
---
drivers/thermal/thermal_sysfs.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index a6f371f..f52708f 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -754,6 +754,9 @@ void thermal_cooling_device_stats_update(struct
thermal_cooling_device *cdev,
{
struct cooling_dev_stats *stats = cdev->stats;
+ if (!stats)
+ return;
+
spin_lock(>lock);
if (stats->state == new_state)
--
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