linux-kernel - Re: [PATCH 4/4] [Patch-next] ACPI, APEI, HEST Fix the unsuitable usage of platform

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Date:	Tue, 17 Aug 2010 12:00:02 +0900
From:	Jin Dongming <jin.dongming@...css.fujitsu.com>
To:	Huang Ying <ying.huang@...el.com>
CC:	Randy Dunlap <randy.dunlap@...cle.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andi Kleen <andi@...stfloor.org>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	ACPI <linux-acpi@...r.kernel.org>,
	LKLM <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] [Patch-next] ACPI, APEI, HEST Fix the unsuitable
 usage of platform_data.

(2010/08/17 10:39), Huang Ying wrote:
> On Tue, 2010-08-17 at 08:58 +0800, Jin Dongming wrote:
>> platform_data in hest_parse_ghes() is used for saving the address of entry
>> information of erst_tab. When the device is failed to be added, platform_data
>> will be freed by platform_device_put(). But the value saved in platform_data
>> should not be freed here. If it is done, it will make system panic.
> 
> Good catch. Thanks.
> 
>> So I think platform_data should save the address of allocated memory
>> which saves entry information of erst_tab.
>>
>> This patch fixed it and I confirmed it on x86_64 next-tree.
>>
>> Signed-off-by: Jin Dongming <jin.dongming@...css.fujitsu.com>
>> ---
>>  drivers/acpi/apei/ghes.c |    2 +-
>>  drivers/acpi/apei/hest.c |   19 ++++++++++++++-----
>>  2 files changed, 15 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>> index 385a605..b35c622 100644
>> --- a/drivers/acpi/apei/ghes.c
>> +++ b/drivers/acpi/apei/ghes.c
>> @@ -302,7 +302,7 @@ static int __devinit ghes_probe(struct platform_device *ghes_dev)
>>  	struct ghes *ghes = NULL;
>>  	int rc = -EINVAL;
>>  
>> -	generic = ghes_dev->dev.platform_data;
>> +	generic = *(struct acpi_hest_generic **)(ghes_dev->dev.platform_data);
>>  	if (!generic->enabled)
>>  		return -ENODEV;
>>  
>> diff --git a/drivers/acpi/apei/hest.c b/drivers/acpi/apei/hest.c
>> index 343168d..5a65e2a 100644
>> --- a/drivers/acpi/apei/hest.c
>> +++ b/drivers/acpi/apei/hest.c
>> @@ -137,20 +137,29 @@ static int hest_parse_ghes_count(struct acpi_hest_header *hest_hdr, void *data)
>>  
>>  static int hest_parse_ghes(struct acpi_hest_header *hest_hdr, void *data)
>>  {
>> -	struct acpi_hest_generic *generic;
>> +	void **platform_data;
>>  	struct platform_device *ghes_dev;
>>  	struct ghes_arr *ghes_arr = data;
>>  	int rc;
>>  
>>  	if (hest_hdr->type != ACPI_HEST_TYPE_GENERIC_ERROR)
>>  		return 0;
>> -	generic = (struct acpi_hest_generic *)hest_hdr;
>> -	if (!generic->enabled)
>> +
>> +	platform_data = kmalloc(sizeof(void *), GFP_KERNEL);
>> +	if (!platform_data)
>> +		return -ENOMEM;
>> +
>> +	*platform_data = hest_hdr;
>> +	if (!((struct acpi_hest_generic *)*platform_data)->enabled)
>>  		return 0;
>> +
>>  	ghes_dev = platform_device_alloc("GHES", hest_hdr->source_id);
>> -	if (!ghes_dev)
>> +	if (!ghes_dev) {
>> +		kfree(platform_data);
>>  		return -ENOMEM;
>> -	ghes_dev->dev.platform_data = generic;
>> +	}
>> +
>> +	ghes_dev->dev.platform_data = platform_data;
>>  	rc = platform_device_add(ghes_dev);
>>  	if (rc)
>>  		goto err;
> 
> Why not use platform_device_add_data?
Here what should be done is to transport the pointer of hest_hdr to platform_data,
so I think that it could be done successfully by allocating 8byte of memory.
If the platform_device_add_data() is used, the more memory will be allocated. 

So I think this method is better than using platform_device_add_data().

> 
> Best Regards,
> Huang Ying
> 
> 
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> 


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