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

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Message-ID: <6bd1b974-1393-5087-b1de-e0d87db023f4@huawei.com>
Date: Sat, 12 Oct 2024 16:14:52 +0800
From: Zheng Zengkai <zhengzengkai@...wei.com>
To: Marc Zyngier <maz@...nel.org>
CC: <lpieralisi@...nel.org>, <guohanjun@...wei.com>, <sudeep.holla@....com>,
	<mark.rutland@....com>, <rafael@...nel.org>, <lenb@...nel.org>,
	<daniel.lezcano@...aro.org>, <tglx@...utronix.de>,
	<linux-acpi@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI: GTDT: Tighten the check for the first platform
 timer entry


在 2024/10/10 23:52, Marc Zyngier 写道:
> On Thu, 10 Oct 2024 15:47:03 +0100,
> Zheng Zengkai <zhengzengkai@...wei.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@...nel.org>
>> Suggested-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
>> Signed-off-by: Zheng Zengkai <zhengzengkai@...wei.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!