acpi_ds_create_field() allocates internal_pcc_buffer for operation
regions in the PCC address space.

The function runs once per field, so a second field on the
same region overwrites the pointer and orphans the previous buffer.

The matching ACPI_FREE() in acpi_ut_delete_internal_obj() only ever sees
the last one.

An arm64 platform whose SSDT declares regions with multiple fields each
leaks two buffers at boot, as detected by kmemleak:

  unreferenced object 0xffff000051e65400 (size 192):
    comm "swapper/0", pid 1, jiffies 4294668436
    backtrace (crc 0):
      __kmalloc_noprof
      acpi_ds_create_field
      acpi_ds_load2_end_op
      acpi_ds_exec_end_op
      acpi_ps_parse_loop
      acpi_ps_parse_aml
      acpi_ns_load_table
      acpi_load_tables
      acpi_init

Do not allocate a region if it was previously allocated before,
preserving the current design, but, not leaking memory.

Fixes: aa6ec56b574d ("ACPICA: ACPI 6.3: add PCC operation region support for AML interpreter")
Link: https://github.com/open-acpica/acpica/commit/c71849d476bb5f97ca1867849e893368e12a69e6
Signed-off-by: Breno Leitao <leitao@debian.org>
---
Changes in v2:
- Got the fix into ACPI CA first, and now respining this one with the
  Link to ACPI CA change.
- Link to v1: https://patch.msgid.link/20260813-acpica-pcc-field-leak-v1-1-3d6c5f0eb557@debian.org
---
 drivers/acpi/acpica/dsfield.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpica/dsfield.c b/drivers/acpi/acpica/dsfield.c
index d7d56cc600d318..f7e503bf57c87c 100644
--- a/drivers/acpi/acpica/dsfield.c
+++ b/drivers/acpi/acpica/dsfield.c
@@ -522,7 +522,8 @@ acpi_ds_create_field(union acpi_parse_object *op,
 	}
 
 	if (info.region_node->object->region.space_id ==
-	    ACPI_ADR_SPACE_PLATFORM_COMM) {
+	    ACPI_ADR_SPACE_PLATFORM_COMM &&
+	    !region_node->object->field.internal_pcc_buffer) {
 		region_node->object->field.internal_pcc_buffer =
 		    ACPI_ALLOCATE_ZEROED(info.region_node->object->region.
 					 length);

---
base-commit: 4c253ac4b29b8c6cc6fdef8f92d4facde62e63b9
change-id: 20260813-acpica-pcc-field-leak-8f676f55179b

Best regards,
--  
Breno Leitao <leitao@debian.org>

On Fri, Sep 25, 2026 at 4:35 PM Breno Leitao <leitao@debian.org> wrote:
>
> acpi_ds_create_field() allocates internal_pcc_buffer for operation
> regions in the PCC address space.
>
> The function runs once per field, so a second field on the
> same region overwrites the pointer and orphans the previous buffer.
>
> The matching ACPI_FREE() in acpi_ut_delete_internal_obj() only ever sees
> the last one.
>
> An arm64 platform whose SSDT declares regions with multiple fields each
> leaks two buffers at boot, as detected by kmemleak:
>
>   unreferenced object 0xffff000051e65400 (size 192):
>     comm "swapper/0", pid 1, jiffies 4294668436
>     backtrace (crc 0):
>       __kmalloc_noprof
>       acpi_ds_create_field
>       acpi_ds_load2_end_op
>       acpi_ds_exec_end_op
>       acpi_ps_parse_loop
>       acpi_ps_parse_aml
>       acpi_ns_load_table
>       acpi_load_tables
>       acpi_init
>
> Do not allocate a region if it was previously allocated before,
> preserving the current design, but, not leaking memory.
>
> Fixes: aa6ec56b574d ("ACPICA: ACPI 6.3: add PCC operation region support for AML interpreter")
> Link: https://github.com/open-acpica/acpica/commit/c71849d476bb5f97ca1867849e893368e12a69e6
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
> Changes in v2:
> - Got the fix into ACPI CA first, and now respining this one with the
>   Link to ACPI CA change.
> - Link to v1: https://patch.msgid.link/20260813-acpica-pcc-field-leak-v1-1-3d6c5f0eb557@debian.org
> ---
>  drivers/acpi/acpica/dsfield.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpica/dsfield.c b/drivers/acpi/acpica/dsfield.c
> index d7d56cc600d318..f7e503bf57c87c 100644
> --- a/drivers/acpi/acpica/dsfield.c
> +++ b/drivers/acpi/acpica/dsfield.c
> @@ -522,7 +522,8 @@ acpi_ds_create_field(union acpi_parse_object *op,
>         }
>
>         if (info.region_node->object->region.space_id ==
> -           ACPI_ADR_SPACE_PLATFORM_COMM) {
> +           ACPI_ADR_SPACE_PLATFORM_COMM &&
> +           !region_node->object->field.internal_pcc_buffer) {
>                 region_node->object->field.internal_pcc_buffer =
>                     ACPI_ALLOCATE_ZEROED(info.region_node->object->region.
>                                          length);
>
> ---

Applied as 7.4 material, thanks!