Re: [PATCH v2] platform/x86/amd: pmf: Use device managed allocations

[Mario Limonciello <superm1@kernel.org>]

On 5/7/2025 4:44 AM, Ilpo Järvinen wrote:
> On Tue, 6 May 2025, Mario Limonciello wrote:
> 
>> From: Mario Limonciello <mario.limonciello@amd.com>
>>
>> If setting up smart PC fails for any reason then this can lead to
>> a double free when unloading amd-pmf.  This is because dev->buf was
>> freed but never set to NULL and is again freed in amd_pmf_remove().
>>
>> To avoid subtle allocation bugs in failures leading to a double free
>> change all allocations into device managed allocations.
>>
>> Fixes: 5b1122fc4995f ("platform/x86/amd/pmf: fix cleanup in amd_pmf_init_smart_pc()")
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v1->v2:
>>   * Correct commit message with correct offending function root cause
>>   * Switch to device managed allocations.
>>
>>   drivers/platform/x86/amd/pmf/core.c   |  3 +--
>>   drivers/platform/x86/amd/pmf/tee-if.c | 30 ++++++++-------------------
>>   2 files changed, 10 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/platform/x86/amd/pmf/core.c b/drivers/platform/x86/amd/pmf/core.c
>> index 96821101ec773..395c011e837f1 100644
>> --- a/drivers/platform/x86/amd/pmf/core.c
>> +++ b/drivers/platform/x86/amd/pmf/core.c
>> @@ -280,7 +280,7 @@ int amd_pmf_set_dram_addr(struct amd_pmf_dev *dev, bool alloc_buffer)
>>   			dev_err(dev->dev, "Invalid CPU id: 0x%x", dev->cpu_id);
>>   		}
>>   
>> -		dev->buf = kzalloc(dev->mtable_size, GFP_KERNEL);
>> +		dev->buf = devm_kzalloc(dev->dev, dev->mtable_size, GFP_KERNEL);
>>   		if (!dev->buf)
>>   			return -ENOMEM;
>>   	}
>> @@ -493,7 +493,6 @@ static void amd_pmf_remove(struct platform_device *pdev)
>>   	mutex_destroy(&dev->lock);
>>   	mutex_destroy(&dev->update_mutex);
>>   	mutex_destroy(&dev->cb_mutex);
>> -	kfree(dev->buf);
>>   }
>>   
>>   static const struct attribute_group *amd_pmf_driver_groups[] = {
>> diff --git a/drivers/platform/x86/amd/pmf/tee-if.c b/drivers/platform/x86/amd/pmf/tee-if.c
>> index d3bd12ad036ae..50c082a78cd9e 100644
>> --- a/drivers/platform/x86/amd/pmf/tee-if.c
>> +++ b/drivers/platform/x86/amd/pmf/tee-if.c
>> @@ -532,13 +532,13 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
>>   	dev->policy_base = devm_ioremap_resource(dev->dev, dev->res);
>>   	if (IS_ERR(dev->policy_base)) {
>>   		ret = PTR_ERR(dev->policy_base);
>> -		goto err_free_dram_buf;
>> +		goto err_cancel_work;
>>   	}
>>   
>> -	dev->policy_buf = kzalloc(dev->policy_sz, GFP_KERNEL);
>> +	dev->policy_buf = devm_kzalloc(dev->dev, dev->policy_sz, GFP_KERNEL);
> 
> Hi Mario,
> 
> Isn't ->policy_buf freed and another allocated in amd_pmf_get_pb_data()
> and this patch lacks any changes around there?? That switch of the buffer
> has been the reason why I've not suggested using devm_*() for earlier for
> it.
> 
> Please check all related code to the pointers you're changing if there
> are other similar traps you have not taken into account.

Ah, thanks I thought I caught them all but missed that instance.

A few options that come to mind:
1) instead make the very first allocation POLICY_BUF_MAX_SZ, and then 
never reallocate for the life of the driver.
2) Don't allow sideloading a bigger policy than the original one in the 
firmware.
3) Don't switch all 3 to device managed like this patch, just switch the 
two that can and fix the one broken one causing a double free.
4) Switch the case you pointed out to use devm_kfree() and re-allocate 
at that time.

Anyone with a preference?  I lean upon option 4.

> 
>>   	if (!dev->policy_buf) {
>>   		ret = -ENOMEM;
>> -		goto err_free_dram_buf;
>> +		goto err_cancel_work;
>>   	}
>>   
>>   	memcpy_fromio(dev->policy_buf, dev->policy_base, dev->policy_sz);
>> @@ -546,21 +546,21 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
>>   	if (!amd_pmf_pb_valid(dev)) {
>>   		dev_info(dev->dev, "No Smart PC policy present\n");
>>   		ret = -EINVAL;
>> -		goto err_free_policy;
>> +		goto err_cancel_work;
>>   	}
>>   
>>   	amd_pmf_hex_dump_pb(dev);
>>   
>> -	dev->prev_data = kzalloc(sizeof(*dev->prev_data), GFP_KERNEL);
>> +	dev->prev_data = devm_kzalloc(dev->dev, sizeof(*dev->prev_data), GFP_KERNEL);
>>   	if (!dev->prev_data) {
>>   		ret = -ENOMEM;
>> -		goto err_free_policy;
>> +		goto err_cancel_work;
>>   	}
>>   
>>   	for (i = 0; i < ARRAY_SIZE(amd_pmf_ta_uuid); i++) {
>>   		ret = amd_pmf_tee_init(dev, &amd_pmf_ta_uuid[i]);
>>   		if (ret)
>> -			goto err_free_prev_data;
>> +			goto err_cancel_work;
>>   
>>   		ret = amd_pmf_start_policy_engine(dev);
>>   		switch (ret) {
>> @@ -575,7 +575,7 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
>>   		default:
>>   			ret = -EINVAL;
>>   			amd_pmf_tee_deinit(dev);
>> -			goto err_free_prev_data;
>> +			goto err_cancel_work;
>>   		}
>>   
>>   		if (status)
>> @@ -584,7 +584,7 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
>>   
>>   	if (!status && !pb_side_load) {
>>   		ret = -EINVAL;
>> -		goto err_free_prev_data;
>> +		goto err_cancel_work;
>>   	}
>>   
>>   	if (pb_side_load)
>> @@ -600,12 +600,6 @@ int amd_pmf_init_smart_pc(struct amd_pmf_dev *dev)
>>   	if (pb_side_load && dev->esbin)
>>   		amd_pmf_remove_pb(dev);
>>   	amd_pmf_tee_deinit(dev);
>> -err_free_prev_data:
>> -	kfree(dev->prev_data);
>> -err_free_policy:
>> -	kfree(dev->policy_buf);
>> -err_free_dram_buf:
>> -	kfree(dev->buf);
>>   err_cancel_work:
>>   	cancel_delayed_work_sync(&dev->pb_work);
>>   
>> @@ -621,11 +615,5 @@ void amd_pmf_deinit_smart_pc(struct amd_pmf_dev *dev)
>>   		amd_pmf_remove_pb(dev);
>>   
>>   	cancel_delayed_work_sync(&dev->pb_work);
>> -	kfree(dev->prev_data);
>> -	dev->prev_data = NULL;
>> -	kfree(dev->policy_buf);
>> -	dev->policy_buf = NULL;
>> -	kfree(dev->buf);
>> -	dev->buf = NULL;
>>   	amd_pmf_tee_deinit(dev);
>>   }
>>
>