coresight: syscfg: Fix memleak on registration failure in cscfg_create_device

PATCH Superseded Miaoqian Lin 2 participants 5 messages Jan 10, 2022 – Feb 1, 2022

Subsystems (2)

Arm/CoreSight framework and drivers Hardware tracing facilities

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Share & tools

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Miaoqian Lin

author

2022-01-10 07:32 UTC #0 lore raw

PATCH 1/1 coresight: syscfg: Fix memleak on registration failure in cscfg_create_device

device_register() calls device_initialize(),
according to doc of device_initialize:

Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.

To prevent potential memleak, use put_device() instead call kfree directly.

Signed-off-by Miaoqian Lin <[email protected]>

---
 drivers/hwtracing/coresight/coresight-syscfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/hwtracing/coresight/coresight-syscfg.c +1 -1

index 43054568430f..007fa1c761a7 100644
@@ -764,7 +764,7 @@ struct device *cscfg_device(void)
 /* Must have a release function or the kernel will complain on module unload */
 static void cscfg_dev_release(struct device *dev)
 {
-	kfree(cscfg_mgr);
+	put_device(dev);
 	cscfg_mgr = NULL;
 }

Signature · 7 lines

2.17.1


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Mathieu Poirier

2022-01-20 17:56 UTC #1 lore raw

Good morning,

Quoted 5 lines · Miaoqian Lin

device_register() calls device_initialize(),
according to doc of device_initialize:
Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.

That is _if_ device_initialize() is called manually. In this instance @dev is registered with device_register() and unregistered with device_unregister(). The latter conforms to the comment you pointed out and calls put_device() as expected.

Thanks,
Mathieu

Quoted 25 lines

To prevent potential memleak, use put_device() instead call kfree directly.

Signed-off-by Miaoqian Lin <[email protected]>

---
 drivers/hwtracing/coresight/coresight-syscfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/hwtracing/coresight/coresight-syscfg.c +1 -1

index 43054568430f..007fa1c761a7 100644
@@ -764,7 +764,7 @@ struct device *cscfg_device(void)
 /* Must have a release function or the kernel will complain on module unload */
 static void cscfg_dev_release(struct device *dev)
 {
-	kfree(cscfg_mgr);
+	put_device(dev);
 	cscfg_mgr = NULL;
 }

Signature · 1 line

2.17.1

Mathieu Poirier

2022-01-20 18:28 UTC #2 lore raw

Quoted 6 lines · Mathieu Poirier

Good morning,
Quoted 3 lines · Miaoqian Lin
device_register() calls device_initialize(),
according to doc of device_initialize:

Quoted 7 lines

Quoted 2 lines
Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.
That is _if_ device_initialize() is called manually. In this instance @dev is registered with device_register() and unregistered with device_unregister(). The latter conforms to the comment you pointed out and calls put_device() as expected.

I originally misunderstood the context - you are referring to the failure path in cscfg_create_device(). You are correct about needing to call put_device() but your solution will not work when the module is unloaded properly and device_unregister() is called by way of cscfg_clear_device(). In that case device_unregister() is already calling put_device().

Here simply calling put_device() instead of cscfg_dev_release() in the error path should do just fine. That will call cscfg_dev_release() and the memory allocated for cscfg_mgr will be release.

Quoted 29 lines

Thanks,
Mathieu
Quoted 25 lines
To prevent potential memleak, use put_device() instead call kfree directly.
Signed-off-by Miaoqian Lin <[email protected]>
---
 drivers/hwtracing/coresight/coresight-syscfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/hwtracing/coresight/coresight-syscfg.c +1 -1
index 43054568430f..007fa1c761a7 100644
@@ -764,7 +764,7 @@ struct device *cscfg_device(void)
 /* Must have a release function or the kernel will complain on module unload */
 static void cscfg_dev_release(struct device *dev)
 {
-	kfree(cscfg_mgr);
+	put_device(dev);
 	cscfg_mgr = NULL;
 }
 
Signature · 1 line
2.17.1

Miaoqian Lin

author

2022-01-24 12:41 UTC #3 lore raw

PATCH v2 1/1 coresight: syscfg: Fix memleak on registration failure in cscfg_create_device

device_register() calls device_initialize(),
according to doc of device_initialize:

Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.

To prevent potential memleak, use put_device() for error handling.

Signed-off-by Miaoqian Lin <[email protected]>

---
Changes in v2:
- simply call put_device() instead of cscfg_dev_release() in the error path of cscfg_create_device.

---
 drivers/hwtracing/coresight/coresight-syscfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/hwtracing/coresight/coresight-syscfg.c +1 -1

index 43054568430f..c30989e0675f 100644
@@ -791,7 +791,7 @@ static int cscfg_create_device(void)
 
 	err = device_register(dev);
 	if (err)
-		cscfg_dev_release(dev);
+		put_device(dev);
 
 create_dev_exit_unlock:
 	mutex_unlock(&cscfg_mutex);

Signature · 1 line

2.17.1

Mathieu Poirier

Applied

2022-02-01 17:13 UTC #4 lore raw

Quoted 22 lines · Miaoqian Lin

device_register() calls device_initialize(),
according to doc of device_initialize:
Use put_device() to give up your reference instead of freeing
* @dev directly once you have called this function.
To prevent potential memleak, use put_device() for error handling.
Signed-off-by Miaoqian Lin <[email protected]>
---
Changes in v2:
- simply call put_device() instead of cscfg_dev_release() in the error path of cscfg_create_device.
---
 drivers/hwtracing/coresight/coresight-syscfg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/hwtracing/coresight/coresight-syscfg.c +0 -0
index 43054568430f..c30989e0675f 100644

drivers/hwtracing/coresight/coresight-syscfg.c static int cscfg_create_device(void) · line 794

Quoted 5 lines

drivers/hwtracing/coresight/coresight-syscfg.c +1 -1

@@ -791,7 +791,7 @@ static int cscfg_create_device(void)
 
 	err = device_register(dev);
 	if (err)
-		cscfg_dev_release(dev);
+		put_device(dev);

Applied.

Thanks,
Mathieu

Quoted 6 lines

drivers/hwtracing/coresight/coresight-syscfg.c +0 -0
 create_dev_exit_unlock:
 	mutex_unlock(&cscfg_mutex);
Signature · 1 line
2.17.1