[PATCH] ACPI: GTDT: Tighten the check for the first platform timer entry

[PATCH] ACPI: GTDT: Tighten the check for the first platform timer entry

[Zheng Zengkai]

As suggested by Marc and Lorenzo, first we need to check whether
the platform_timer pointer is within gtdt bounds (< gtdt_end) before
de-referencing what it points at to detect the (first) platform
timer entry length and check that next platform_timer pointer is
within gtdt_end too. Now we do that only in next_platform_timer()
for subsequent platform timers.

So add check against table length (gtdt_end) for the first platform
timer entry.

Suggested-by: Marc Zyngier <maz@kernel.org>
Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
---
 drivers/acpi/arm64/gtdt.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
index c0e77c1c8e09..f249af1ed1cd 100644
--- a/drivers/acpi/arm64/gtdt.c
+++ b/drivers/acpi/arm64/gtdt.c
@@ -177,7 +177,8 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
 	}
 
 	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
-	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
+	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt) ||
+			platform_timer >= acpi_gtdt_desc.gtdt_end) {
 		pr_err(FW_BUG "invalid timer data.\n");
 		return -EINVAL;
 	}
-- 
2.20.1

Re: [PATCH] ACPI: GTDT: Tighten the check for the first platform timer entry

[Marc Zyngier]

On Thu, 10 Oct 2024 15:47:03 +0100,
Zheng Zengkai <zhengzengkai@huawei.com> wrote:
> 
> As suggested by Marc and Lorenzo, first we need to check whether
> the platform_timer pointer is within gtdt bounds (< gtdt_end) before
> de-referencing what it points at to detect the (first) platform
> timer entry length and check that next platform_timer pointer is
> within gtdt_end too. Now we do that only in next_platform_timer()
> for subsequent platform timers.
> 
> So add check against table length (gtdt_end) for the first platform
> timer entry.
> 
> Suggested-by: Marc Zyngier <maz@kernel.org>
> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
> ---
>  drivers/acpi/arm64/gtdt.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
> index c0e77c1c8e09..f249af1ed1cd 100644
> --- a/drivers/acpi/arm64/gtdt.c
> +++ b/drivers/acpi/arm64/gtdt.c
> @@ -177,7 +177,8 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>  	}
>  
>  	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
> -	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
> +	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt) ||
> +			platform_timer >= acpi_gtdt_desc.gtdt_end) {
>  		pr_err(FW_BUG "invalid timer data.\n");
>  		return -EINVAL;
>  	}

You  are  only  checking  the  base  pointer  for  the  platform_timer
array. This doesn't say anything about the *size* of that array (or at
least its first element), and whether that actually fits in the table.

	M.

-- 
Without deviation from the norm, progress is not possible.

Re: [PATCH] ACPI: GTDT: Tighten the check for the first platform timer entry

[Zheng Zengkai]

在 2024/10/10 23:52, Marc Zyngier 写道:
> On Thu, 10 Oct 2024 15:47:03 +0100,
> Zheng Zengkai <zhengzengkai@huawei.com> wrote:
>> As suggested by Marc and Lorenzo, first we need to check whether
>> the platform_timer pointer is within gtdt bounds (< gtdt_end) before
>> de-referencing what it points at to detect the (first) platform
>> timer entry length and check that next platform_timer pointer is
>> within gtdt_end too. Now we do that only in next_platform_timer()
>> for subsequent platform timers.
>>
>> So add check against table length (gtdt_end) for the first platform
>> timer entry.
>>
>> Suggested-by: Marc Zyngier <maz@kernel.org>
>> Suggested-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
>> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
>> ---
>>   drivers/acpi/arm64/gtdt.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
>> index c0e77c1c8e09..f249af1ed1cd 100644
>> --- a/drivers/acpi/arm64/gtdt.c
>> +++ b/drivers/acpi/arm64/gtdt.c
>> @@ -177,7 +177,8 @@ int __init acpi_gtdt_init(struct acpi_table_header *table,
>>   	}
>>   
>>   	platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
>> -	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt)) {
>> +	if (platform_timer < (void *)table + sizeof(struct acpi_table_gtdt) ||
>> +			platform_timer >= acpi_gtdt_desc.gtdt_end) {
>>   		pr_err(FW_BUG "invalid timer data.\n");
>>   		return -EINVAL;
>>   	}
> You  are  only  checking  the  base  pointer  for  the  platform_timer
> array. This doesn't say anything about the *size* of that array (or at
> least its first element), and whether that actually fits in the table.
>
> 	M.


Yes, I will send v2 to check against gtdt_end for both entry and length

of each array element.

Thanks!