Re: [PATCH v4] ACPI: GTDT: Tighten the check for the array of platform timer structures

[Zheng Zengkai <zhengzengkai@huawei.com>]

Gentle ping.

This patch still can be applied to upstream now.

Thanks!


在 2024/10/16 18:01, Lorenzo Pieralisi 写道:
> On Wed, Oct 16, 2024 at 05:54:58PM +0800, Zheng Zengkai wrote:
>> As suggested by Marc and Lorenzo, first we need to check whether the
>> platform_timer entry pointer is within gtdt bounds (< gtdt_end) before
>> de-referencing what it points at to detect the length of the platform
>> timer struct and then check that the length of current platform_timer
>> struct is also valid, i.e. the length is not zero and within gtdt_end.
>> Now next_platform_timer() only checks against gtdt_end for the entry of
>> subsequent platform timer without checking the length of it and will
>> not report error if the check failed and the existing check in function
>> acpi_gtdt_init() is also not enough.
>>
>> Modify the for_each_platform_timer() iterator and use it combined with
>> a dedicated check function platform_timer_valid() to do the check
>> against table length (gtdt_end) for each element of platform timer
>> array in function acpi_gtdt_init(), making sure that both their entry
>> and length actually fit in the table.
>>
>> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>> Co-developed-by: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
>> ---
>> Changes in v4:
>> - remove the tmp pointer to make the code more concise.
>>
>> Changes in v3:
>> - based on Marc's patch and reuse the for_each_platform_timer() loop
>> Link to v3: https://lore.kernel.org/linux-arm-kernel/20241015152602.184108-1-zhengzengkai@huawei.com/
>>
>> Changes in v2:
>> - Check against gtdt_end for both entry and len of each array element
>> Link to v2: https://lore.kernel.org/linux-arm-kernel/20241012085343.6594-1-zhengzengkai@huawei.com/
>>
>> Link to v1: https://lore.kernel.org/all/20241010144703.113728-1-zhengzengkai@huawei.com/
>>
>> Link to previous related patches:
>> https://lore.kernel.org/all/20241008082429.33646-1-zhengzengkai@huawei.com/
>> https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/
>> ---
>>   drivers/acpi/arm64/gtdt.c | 29 ++++++++++++++++++++---------
>>   1 file changed, 20 insertions(+), 9 deletions(-)
> Reviewed-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>
>> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
>> index c0e77c1c8e09..d7c4e1b9915b 100644
>> --- a/drivers/acpi/arm64/gtdt.c
>> +++ b/drivers/acpi/arm64/gtdt.c
>> @@ -36,19 +36,25 @@ struct acpi_gtdt_descriptor {
>>   
>>   static struct acpi_gtdt_descriptor acpi_gtdt_desc __initdata;
>>   
>> -static inline __init void *next_platform_timer(void *platform_timer)
>> +static __init bool platform_timer_valid(void *platform_timer)
>>   {
>>   	struct acpi_gtdt_header *gh = platform_timer;
>>   
>> -	platform_timer += gh->length;
>> -	if (platform_timer < acpi_gtdt_desc.gtdt_end)
>> -		return platform_timer;
>> +	return (platform_timer >= (void *)(acpi_gtdt_desc.gtdt + 1) &&
>> +		platform_timer < acpi_gtdt_desc.gtdt_end &&
>> +		gh->length != 0 &&
>> +		platform_timer + gh->length <= acpi_gtdt_desc.gtdt_end);
>> +}
>> +
>> +static __init void *next_platform_timer(void *platform_timer)
>> +{
>> +	struct acpi_gtdt_header *gh = platform_timer;
>>   
>> -	return NULL;
>> +	return platform_timer + gh->length;
>>   }
>>   
>>   #define for_each_platform_timer(_g)				\
>> -	for (_g = acpi_gtdt_desc.platform_timer; _g;	\
>> +	for (_g = acpi_gtdt_desc.platform_timer; platform_timer_valid(_g);\
>>   	     _g = next_platform_timer(_g))
>>   
>>   static inline bool is_timer_block(void *platform_timer)
>> @@ -157,6 +163,7 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>>   {
>>   	void *platform_timer;
>>   	struct acpi_table_gtdt *gtdt;
>> +	int cnt = 0;
>>   
>>   	gtdt = container_of(table, struct acpi_table_gtdt, header);
>>   	acpi_gtdt_desc.gtdt = gtdt;
>> @@ -176,12 +183,16 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>>   		return 0;
>>   	}
>>   
>> -	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
>> -	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
>> +	acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
>> +	for_each_platform_timer(platform_timer)
>> +		cnt++;
>> +
>> +	if (cnt != gtdt->platform_timer_count) {
>> +		acpi_gtdt_desc.platform_timer = NULL;
>>   		pr_err(FW_BUG "invalid timer data.\n");
>>   		return -EINVAL;
>>   	}
>> -	acpi_gtdt_desc.platform_timer = platform_timer;
>> +
>>   	if (platform_timer_count)
>>   		*platform_timer_count = gtdt->platform_timer_count;
>>   
>> -- 
>> 2.20.1
>>
> .
>