[PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Krzysztof Kozlowski]

During unbinding the driver was dereferencing a pointer to memory
already freed by power_supply_unregister().

Driver was freeing its internal description of battery through pointers
stored in power_supply structure. However, because the core owns the
power supply instance, after calling power_supply_unregister() the
driver cannot access these members.

Fix this by using resource-managed allocations so internal data will be
freed by pointers stored in resource-managed core.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reported-by: H.J. Lu <hjl.tools@gmail.com>
Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
Cc: <stable@vger.kernel.org>
---
 drivers/hid/hid-input.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 14aebe483219..5429a8497d51 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -408,15 +408,14 @@ static bool hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 	if (dev->battery != NULL)
 		goto out;	/* already initialized? */
 
-	psy_desc = kzalloc(sizeof(*psy_desc), GFP_KERNEL);
+	psy_desc = devm_kzalloc(&dev->dev, sizeof(*psy_desc), GFP_KERNEL);
 	if (psy_desc == NULL)
 		goto out;
 
-	psy_desc->name = kasprintf(GFP_KERNEL, "hid-%s-battery", dev->uniq);
-	if (psy_desc->name == NULL) {
-		kfree(psy_desc);
+	psy_desc->name = devm_kasprintf(&dev->dev, GFP_KERNEL,
+					"hid-%s-battery", dev->uniq);
+	if (psy_desc->name == NULL)
 		goto out;
-	}
 
 	psy_desc->type = POWER_SUPPLY_TYPE_BATTERY;
 	psy_desc->properties = hidinput_battery_props;
@@ -449,8 +448,6 @@ static bool hidinput_setup_battery(struct hid_device *dev, unsigned report_type,
 	if (IS_ERR(dev->battery)) {
 		hid_warn(dev, "can't register power supply: %ld\n",
 				PTR_ERR(dev->battery));
-		kfree(psy_desc->name);
-		kfree(psy_desc);
 		dev->battery = NULL;
 	} else {
 		power_supply_powers(dev->battery, &dev->dev);
@@ -466,8 +463,6 @@ static void hidinput_cleanup_battery(struct hid_device *dev)
 		return;
 
 	power_supply_unregister(dev->battery);
-	kfree(dev->battery->desc->name);
-	kfree(dev->battery->desc);
 	dev->battery = NULL;
 }
 #else  /* !CONFIG_HID_BATTERY_STRENGTH */
-- 
1.9.1

Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Jiri Kosina]

On Tue, 28 Jul 2015, Krzysztof Kozlowski wrote:

> During unbinding the driver was dereferencing a pointer to memory
> already freed by power_supply_unregister().
> 
> Driver was freeing its internal description of battery through pointers
> stored in power_supply structure. However, because the core owns the
> power supply instance, after calling power_supply_unregister() the
> driver cannot access these members.
> 
> Fix this by using resource-managed allocations so internal data will be
> freed by pointers stored in resource-managed core.
> 
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> Reported-by: H.J. Lu <hjl.tools@gmail.com>
> Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
> Cc: <stable@vger.kernel.org>

Applied to for-4.2/upstream-fixes, thanks.

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Dmitry Torokhov]

On Wed, Jul 29, 2015 at 03:07:04PM +0200, Jiri Kosina wrote:
> On Tue, 28 Jul 2015, Krzysztof Kozlowski wrote:
> 
> > During unbinding the driver was dereferencing a pointer to memory
> > already freed by power_supply_unregister().
> > 
> > Driver was freeing its internal description of battery through pointers
> > stored in power_supply structure. However, because the core owns the
> > power supply instance, after calling power_supply_unregister() the
> > driver cannot access these members.
> > 
> > Fix this by using resource-managed allocations so internal data will be
> > freed by pointers stored in resource-managed core.
> > 
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> > Reported-by: H.J. Lu <hjl.tools@gmail.com>
> > Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
> > Cc: <stable@vger.kernel.org>
> 
> Applied to for-4.2/upstream-fixes, thanks.

Wait, what guarantees do we have that this is only called in probe()
paths? Don't we allow hid_hw_start() be deferred to open() calls?

In general we need to be careful with devm* conversions in core code.

Thanks.

-- 
Dmitry

Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Krzysztof Kozlowski]

2015-07-30 2:46 GMT+09:00 Dmitry Torokhov <dmitry.torokhov@gmail.com>:
> On Wed, Jul 29, 2015 at 03:07:04PM +0200, Jiri Kosina wrote:
>> On Tue, 28 Jul 2015, Krzysztof Kozlowski wrote:
>>
>> > During unbinding the driver was dereferencing a pointer to memory
>> > already freed by power_supply_unregister().
>> >
>> > Driver was freeing its internal description of battery through pointers
>> > stored in power_supply structure. However, because the core owns the
>> > power supply instance, after calling power_supply_unregister() the
>> > driver cannot access these members.
>> >
>> > Fix this by using resource-managed allocations so internal data will be
>> > freed by pointers stored in resource-managed core.
>> >
>> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>> > Reported-by: H.J. Lu <hjl.tools@gmail.com>
>> > Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
>> > Cc: <stable@vger.kernel.org>
>>
>> Applied to for-4.2/upstream-fixes, thanks.
>
> Wait, what guarantees do we have that this is only called in probe()
> paths? Don't we allow hid_hw_start() be deferred to open() calls?

Indeed, this may be called in other contexts. But this should not
introduce errors except not reclaimable memory (till remove()
happens).

> In general we need to be careful with devm* conversions in core code.
>

Another and less intrusive fix would be:

    char *name = dev->battery->desc->name;
    struct power_supply_desc *psy_desc = dev->battery->desc;
    power_supply_unregister(dev->battery);
    kfree(name);
    kfree(psy_desc);

How about this?

Best regards,
Krzysztof

Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Dmitry Torokhov]

On Thu, Jul 30, 2015 at 08:42:12AM +0900, Krzysztof Kozlowski wrote:
> 2015-07-30 2:46 GMT+09:00 Dmitry Torokhov <dmitry.torokhov@gmail.com>:
> > On Wed, Jul 29, 2015 at 03:07:04PM +0200, Jiri Kosina wrote:
> >> On Tue, 28 Jul 2015, Krzysztof Kozlowski wrote:
> >>
> >> > During unbinding the driver was dereferencing a pointer to memory
> >> > already freed by power_supply_unregister().
> >> >
> >> > Driver was freeing its internal description of battery through pointers
> >> > stored in power_supply structure. However, because the core owns the
> >> > power supply instance, after calling power_supply_unregister() the
> >> > driver cannot access these members.
> >> >
> >> > Fix this by using resource-managed allocations so internal data will be
> >> > freed by pointers stored in resource-managed core.
> >> >
> >> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> >> > Reported-by: H.J. Lu <hjl.tools@gmail.com>
> >> > Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
> >> > Cc: <stable@vger.kernel.org>
> >>
> >> Applied to for-4.2/upstream-fixes, thanks.
> >
> > Wait, what guarantees do we have that this is only called in probe()
> > paths? Don't we allow hid_hw_start() be deferred to open() calls?
> 
> Indeed, this may be called in other contexts. But this should not
> introduce errors except not reclaimable memory (till remove()
> happens).
> 
> > In general we need to be careful with devm* conversions in core code.
> >
> 
> Another and less intrusive fix would be:
> 
>     char *name = dev->battery->desc->name;
>     struct power_supply_desc *psy_desc = dev->battery->desc;
>     power_supply_unregister(dev->battery);
>     kfree(name);
>     kfree(psy_desc);

I would much rather prefer this to the other version as it does not
leave memory hanging around, potentially indefinitely, but ultimately it
is up to Jiri. I only hope that power supply code does not reference
power_supply_desc pointer past unregister (since the device structure
itself may live past the point where power_supply_unregister() returns).

By the way, you do not need name temp, you can do

	kfree(psy_desc->name);
	kfree(psy_desc);

Thanks.

-- 
Dmitry

Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Jiri Kosina]

On Wed, 29 Jul 2015, Dmitry Torokhov wrote:

> > Another and less intrusive fix would be:
> > 
> >     char *name = dev->battery->desc->name;
> >     struct power_supply_desc *psy_desc = dev->battery->desc;
> >     power_supply_unregister(dev->battery);
> >     kfree(name);
> >     kfree(psy_desc);
> 
> I would much rather prefer this to the other version as it does not
> leave memory hanging around, potentially indefinitely, but ultimately it
> is up to Jiri. 

I must have been in some broken state of mind when applying the original 
one, thanks a lot for catching my brainfart, Dmitry!

Kryzstof, could you please send me properly formatted patch with the 
above, on top of your previous fix?

Thanks.

-- 
Jiri Kosina
SUSE Labs

Re: [PATCH] HID: hid-input: Fix accessing freed memory during driver unbind

[Krzysztof Kozlowski]

2015-08-01 21:11 GMT+09:00 Jiri Kosina <jkosina@suse.com>:
> On Wed, 29 Jul 2015, Dmitry Torokhov wrote:
>
>> > Another and less intrusive fix would be:
>> >
>> >     char *name = dev->battery->desc->name;
>> >     struct power_supply_desc *psy_desc = dev->battery->desc;
>> >     power_supply_unregister(dev->battery);
>> >     kfree(name);
>> >     kfree(psy_desc);
>>
>> I would much rather prefer this to the other version as it does not
>> leave memory hanging around, potentially indefinitely, but ultimately it
>> is up to Jiri.
>
> I must have been in some broken state of mind when applying the original
> one, thanks a lot for catching my brainfart, Dmitry!
>
> Kryzstof, could you please send me properly formatted patch with the
> above, on top of your previous fix?


Of course, I'll send next version.

Best regards,
Krzysztof