diff mbox series

[v4] drm/i915/hwmon: Get rid of devm

Message ID 20240417051642.788740-1-ashutosh.dixit@intel.com (mailing list archive)
State Handled Elsewhere
Headers show
Series [v4] drm/i915/hwmon: Get rid of devm | expand

Commit Message

Dixit, Ashutosh April 17, 2024, 5:16 a.m. UTC
When both hwmon and hwmon drvdata (on which hwmon depends) are device
managed resources, the expectation, on device unbind, is that hwmon will be
released before drvdata. However, in i915 there are two separate code
paths, which both release either drvdata or hwmon and either can be
released before the other. These code paths (for device unbind) are as
follows (see also the bug referenced below):

Call Trace:
release_nodes+0x11/0x70
devres_release_group+0xb2/0x110
component_unbind_all+0x8d/0xa0
component_del+0xa5/0x140
intel_pxp_tee_component_fini+0x29/0x40 [i915]
intel_pxp_fini+0x33/0x80 [i915]
i915_driver_remove+0x4c/0x120 [i915]
i915_pci_remove+0x19/0x30 [i915]
pci_device_remove+0x32/0xa0
device_release_driver_internal+0x19c/0x200
unbind_store+0x9c/0xb0

and

Call Trace:
release_nodes+0x11/0x70
devres_release_all+0x8a/0xc0
device_unbind_cleanup+0x9/0x70
device_release_driver_internal+0x1c1/0x200
unbind_store+0x9c/0xb0

This means that in i915, if use devm, we cannot gurantee that hwmon will
always be released before drvdata. Which means that we have a uaf if hwmon
sysfs is accessed when drvdata has been released but hwmon hasn't.

The only way out of this seems to be do get rid of devm_ and release/free
everything explicitly during device unbind.

v2: Change commit message and other minor code changes
v3: Cleanup from i915_hwmon_register on error (Armin Wolf)
v4: Eliminate potential static analyzer warning (Rodrigo)
    Eliminate fetch_and_zero (Jani)

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10366
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
---
 drivers/gpu/drm/i915/i915_hwmon.c | 52 +++++++++++++++++++++----------
 1 file changed, 36 insertions(+), 16 deletions(-)

Comments

Andi Shyti April 17, 2024, 8:28 a.m. UTC | #1
Hi Ashutosh,

> @@ -839,16 +837,38 @@ void i915_hwmon_register(struct drm_i915_private *i915)
>  		if (!hwm_gt_is_visible(ddat_gt, hwmon_energy, hwmon_energy_input, 0))
>  			continue;
>  
> -		hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat_gt->name,
> -								 ddat_gt,
> -								 &hwm_gt_chip_info,
> -								 NULL);
> -		if (!IS_ERR(hwmon_dev))
> -			ddat_gt->hwmon_dev = hwmon_dev;
> +		hwmon_dev = hwmon_device_register_with_info(dev, ddat_gt->name,
> +							    ddat_gt,
> +							    &hwm_gt_chip_info,
> +							    NULL);
> +		if (IS_ERR(hwmon_dev))
> +			goto err;

here the logic is changing, though. Before we were not leaving if
hwmon_device_register_with_info() was returning error.

Is this wanted? And why isn't it described in the log?

Thanks,
Andi

> +
> +		ddat_gt->hwmon_dev = hwmon_dev;
>  	}
Dixit, Ashutosh April 17, 2024, 3:01 p.m. UTC | #2
On Wed, 17 Apr 2024 01:28:48 -0700, Andi Shyti wrote:
>

Hi Andi,

> > @@ -839,16 +837,38 @@ void i915_hwmon_register(struct drm_i915_private *i915)
> >		if (!hwm_gt_is_visible(ddat_gt, hwmon_energy, hwmon_energy_input, 0))
> >			continue;
> >
> > -		hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat_gt->name,
> > -								 ddat_gt,
> > -								 &hwm_gt_chip_info,
> > -								 NULL);
> > -		if (!IS_ERR(hwmon_dev))
> > -			ddat_gt->hwmon_dev = hwmon_dev;
> > +		hwmon_dev = hwmon_device_register_with_info(dev, ddat_gt->name,
> > +							    ddat_gt,
> > +							    &hwm_gt_chip_info,
> > +							    NULL);
> > +		if (IS_ERR(hwmon_dev))
> > +			goto err;
>
> here the logic is changing, though. Before we were not leaving if
> hwmon_device_register_with_info() was returning error.
>
> Is this wanted? And why isn't it described in the log?

Not sure if the previous logic was intentional or not, anyway I have
restored it in v5 (where I once again forgot to add "PATCH v5" to the
Subject but v5 is there in the version log :/).

Thanks.
--
Ashutosh
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/i915_hwmon.c b/drivers/gpu/drm/i915/i915_hwmon.c
index b758fd110c20..1551a40a675e 100644
--- a/drivers/gpu/drm/i915/i915_hwmon.c
+++ b/drivers/gpu/drm/i915/i915_hwmon.c
@@ -793,7 +793,7 @@  void i915_hwmon_register(struct drm_i915_private *i915)
 	if (!IS_DGFX(i915))
 		return;
 
-	hwmon = devm_kzalloc(dev, sizeof(*hwmon), GFP_KERNEL);
+	hwmon = kzalloc(sizeof(*hwmon), GFP_KERNEL);
 	if (!hwmon)
 		return;
 
@@ -819,14 +819,12 @@  void i915_hwmon_register(struct drm_i915_private *i915)
 	hwm_get_preregistration_info(i915);
 
 	/*  hwmon_dev points to device hwmon<i> */
-	hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat->name,
-							 ddat,
-							 &hwm_chip_info,
-							 hwm_groups);
-	if (IS_ERR(hwmon_dev)) {
-		i915->hwmon = NULL;
-		return;
-	}
+	hwmon_dev = hwmon_device_register_with_info(dev, ddat->name,
+						    ddat,
+						    &hwm_chip_info,
+						    hwm_groups);
+	if (IS_ERR(hwmon_dev))
+		goto err;
 
 	ddat->hwmon_dev = hwmon_dev;
 
@@ -839,16 +837,38 @@  void i915_hwmon_register(struct drm_i915_private *i915)
 		if (!hwm_gt_is_visible(ddat_gt, hwmon_energy, hwmon_energy_input, 0))
 			continue;
 
-		hwmon_dev = devm_hwmon_device_register_with_info(dev, ddat_gt->name,
-								 ddat_gt,
-								 &hwm_gt_chip_info,
-								 NULL);
-		if (!IS_ERR(hwmon_dev))
-			ddat_gt->hwmon_dev = hwmon_dev;
+		hwmon_dev = hwmon_device_register_with_info(dev, ddat_gt->name,
+							    ddat_gt,
+							    &hwm_gt_chip_info,
+							    NULL);
+		if (IS_ERR(hwmon_dev))
+			goto err;
+
+		ddat_gt->hwmon_dev = hwmon_dev;
 	}
+	return;
+err:
+	i915_hwmon_unregister(i915);
 }
 
 void i915_hwmon_unregister(struct drm_i915_private *i915)
 {
-	fetch_and_zero(&i915->hwmon);
+	struct i915_hwmon *hwmon = i915->hwmon;
+	struct intel_gt *gt;
+	int i;
+
+	if (!hwmon)
+		return;
+
+	for_each_gt(gt, i915, i)
+		if (hwmon->ddat_gt[i].hwmon_dev)
+			hwmon_device_unregister(hwmon->ddat_gt[i].hwmon_dev);
+
+	if (hwmon->ddat.hwmon_dev)
+		hwmon_device_unregister(hwmon->ddat.hwmon_dev);
+
+	mutex_destroy(&hwmon->hwmon_lock);
+
+	kfree(i915->hwmon);
+	i915->hwmon = NULL;
 }