[v3] ACPI: GTDT: Tighten the check for the array of platform timer structures

Commit Message

Zheng Zengkai Oct. 15, 2024, 3:26 p.m. UTC

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 <[e-mail]>
Co-developed-by: Marc Zyngier <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Signed-off-by: Zheng Zengkai <[e-mail]>
---
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/[e-mail]/

Link to v1: https://lore.kernel.org/all/[e-mail]/
---
 drivers/acpi/arm64/gtdt.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

Comments

Lorenzo Pieralisi Oct. 15, 2024, 4:44 p.m. UTC | #1

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.

> 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 <[e-mail]>
> Co-developed-by: Marc Zyngier <[e-mail]>
> Signed-off-by: Marc Zyngier <[e-mail]>
> Signed-off-by: Zheng Zengkai <[e-mail]>
> ---
> 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/[e-mail]/
> 
> Link to v1: https://lore.kernel.org/all/[e-mail]/
> ---
>  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

	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 <[e-mail]>

(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
>

Zheng Zengkai Oct. 16, 2024, 8:49 a.m. UTC | #2

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/[e-mail]/


>> 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 <[e-mail]>
>> Co-developed-by: Marc Zyngier <[e-mail]>
>> Signed-off-by: Marc Zyngier <[e-mail]>
>> Signed-off-by: Zheng Zengkai <[e-mail]>
>> ---
>> 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/[e-mail]/
>>
>> Link to v1: https://lore.kernel.org/all/[e-mail]/
>> ---
>>   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 <[e-mail]>
>
> (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
>>
> .
>

Lorenzo Pieralisi Oct. 16, 2024, 9:49 a.m. UTC | #3

On Wed, Oct 16, 2024 at 04:49:36PM +0800, Zheng Zengkai wrote:
> 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/[e-mail]/

No, it was just a comment referring to "As suggested by Marc and Lorenzo",
that's clear from the tags and a Link: to this thread will be added when
the patch is applied (though you can add it too, it would not hurt).

Never mind.

Lorenzo

> > > 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 <[e-mail]>
> > > Co-developed-by: Marc Zyngier <[e-mail]>
> > > Signed-off-by: Marc Zyngier <[e-mail]>
> > > Signed-off-by: Zheng Zengkai <[e-mail]>
> > > ---
> > > 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/[e-mail]/
> > > 
> > > Link to v1: https://lore.kernel.org/all/[e-mail]/
> > > ---
> > >   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 <[e-mail]>
> > 
> > (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
> > > 
> > .
> >

Patch

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;
 	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)