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Message-ID: <4cea2a07-49b0-7703-4cdf-49ded9a2c9e4@huawei.com>
Date: Wed, 16 Oct 2024 16:49:36 +0800
From: Zheng Zengkai <zhengzengkai@...wei.com>
To: Lorenzo Pieralisi <lpieralisi@...nel.org>
CC: <guohanjun@...wei.com>, <sudeep.holla@....com>, <mark.rutland@....com>,
<maz@...nel.org>, <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 v3] ACPI: GTDT: Tighten the check for the array of
platform timer structures
Hi Lorenzo,
在 2024/10/16 0:44, Lorenzo Pieralisi 写道:
> On Tue, Oct 15, 2024 at 11:26:02PM +0800, Zheng Zengkai wrote:
>> As suggested by Marc and Lorenzo, first we need to check whether the
> I would just describe the change, the tags and Link: are there to
> describe this patch history.
Do you mean that the previous patch below also need to be listed in this
change log history?
https://lore.kernel.org/all/20240930030716.179992-1-zhengzengkai@huawei.com/
>> 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@...nel.org>
>> Co-developed-by: Marc Zyngier <maz@...nel.org>
>> Signed-off-by: Marc Zyngier <maz@...nel.org>
>> Signed-off-by: Zheng Zengkai <zhengzengkai@...wei.com>
>> ---
>> Changes in v3:
>> - based on Marc's patch and reuse the for_each_platform_timer() loop
>>
>> 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/
>> ---
>> drivers/acpi/arm64/gtdt.c | 32 +++++++++++++++++++++-----------
>> 1 file changed, 21 insertions(+), 11 deletions(-)
>>
>> diff --git a/drivers/acpi/arm64/gtdt.c b/drivers/acpi/arm64/gtdt.c
>> index c0e77c1c8e09..3583c99afb0d 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; \
>> +#define for_each_platform_timer(_g, first_entry) \
>> + for (_g = first_entry; platform_timer_valid(_g); \
>> _g = next_platform_timer(_g))
>>
>> static inline bool is_timer_block(void *platform_timer)
>> @@ -155,8 +161,9 @@ bool __init acpi_gtdt_c3stop(int type)
>> int __init acpi_gtdt_init(struct acpi_table_header *table,
>> int *platform_timer_count)
>> {
>> - void *platform_timer;
>> + void *platform_timer, *tmp;
> It makes more sense - thank you and Marc.
>
> Nit: you don't really need another pointer (ie tmp) but you may keep
> it if that makes the code clearer - all you need to do is using
> platform_timer as an iterator and initialize
Yes, the tmp pointer can be removed for conciseness.
Thanks!
>
> acpi_gtdt_desc.platform_timer = (void *)gtdt + gtdt->platform_timer_offset;
>
> if all checks passed (you are using tmp just because after the loop
> platform_timer can't be used to initialize acpi_gtdt_desc.platform_timer).
>
> Reviewed-by: Lorenzo Pieralisi <lpieralisi@...nel.org>
>
> (now let's see if this survives GTDTs out there :))
>> struct acpi_table_gtdt *gtdt;
>> + int cnt = 0;
>>
>> gtdt = container_of(table, struct acpi_table_gtdt, header);
>> acpi_gtdt_desc.gtdt = gtdt;
>> @@ -177,7 +184,10 @@ 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)) {
>> + for_each_platform_timer(tmp, platform_timer)
>> + cnt++;
>> +
>> + if (cnt != gtdt->platform_timer_count) {
>> pr_err(FW_BUG "invalid timer data.\n");
>> return -EINVAL;
>> }
>> @@ -305,7 +315,7 @@ int __init acpi_arch_timer_mem_init(struct arch_timer_mem *timer_mem,
>> void *platform_timer;
>>
>> *timer_count = 0;
>> - for_each_platform_timer(platform_timer) {
>> + for_each_platform_timer(platform_timer, acpi_gtdt_desc.platform_timer) {
>> if (is_timer_block(platform_timer)) {
>> ret = gtdt_parse_timer_block(platform_timer, timer_mem);
>> if (ret)
>> @@ -398,7 +408,7 @@ static int __init gtdt_sbsa_gwdt_init(void)
>> if (ret || !timer_count)
>> goto out_put_gtdt;
>>
>> - for_each_platform_timer(platform_timer) {
>> + for_each_platform_timer(platform_timer, acpi_gtdt_desc.platform_timer) {
>> if (is_non_secure_watchdog(platform_timer)) {
>> ret = gtdt_import_sbsa_gwdt(platform_timer, gwdt_count);
>> if (ret)
>> --
>> 2.20.1
>>
> .
>
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