Re: [PATCH v4] ACPI: pfr_update: fix stack buffer overflow in query_capability()

On Fri, Aug 14, 2026 at 10:06 PM Anirudh Prasad <[email protected]> wrote:
>
> query_capability() copies four ACPI buffer objects returned by the
> firmware _DSM into fixed-size u8[16] fields in struct
> pfru_update_cap_info using memcpy with the firmware-supplied length:
>
>   memcpy(&cap_hdr->code_type,
>          elements[CAP_CODE_TYPE_IDX].buffer.pointer,
>          elements[CAP_CODE_TYPE_IDX].buffer.length);
>
> The same pattern repeats for drv_type, platform_id, and oem_id.
> If the firmware returns buffer.length > 16 for any of these fields,
> memcpy writes past the destination array.
>
> struct pfru_update_cap_info is stack-allocated in pfru_ioctl().
> Confirmed with KASAN on 7.2-rc6: three stack-out-of-bounds reports
> are generated when a DSM returns 64-byte buffers, with writes reaching
> 44 bytes past the end of cap_hdr's [64, 156) frame window into
> adjacent stack redzones.
>
> Introduce a helper pointer to out_obj->package.elements and use it
> to validate each buffer length against its destination field size
> before copying, returning -EINVAL if the firmware supplies an
> oversized buffer.
>
> Fixes: 0db89fa243e5 ("ACPI: Introduce Platform Firmware Runtime Update device driver")
> Cc: [email protected]
> Signed-off-by: Anirudh Prasad <[email protected]>

Applied as 7.3-rc material, thanks!

> ---
>  drivers/acpi/pfr_update.c | 45 +++++++++++++++++++++------------------
>  1 file changed, 24 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/acpi/pfr_update.c b/drivers/acpi/pfr_update.c
> index 6283105bb0e8..9afd2c52fdbd 100644
> --- a/drivers/acpi/pfr_update.c
> +++ b/drivers/acpi/pfr_update.c
> @@ -120,7 +120,7 @@ static int query_capability(struct pfru_update_cap_info *cap_hdr,
>                             struct pfru_device *pfru_dev)
>  {
>         acpi_handle handle = ACPI_HANDLE(pfru_dev->parent_dev);
> -       union acpi_object *out_obj;
> +       union acpi_object *out_obj, *elem;
>         int ret = -EINVAL;
>
>         out_obj = acpi_evaluate_dsm_typed(handle, &pfru_guid,
> @@ -150,7 +150,9 @@ static int query_capability(struct pfru_update_cap_info *cap_hdr,
>                 goto free_acpi_buffer;
>         }
>
> -       cap_hdr->status = out_obj->package.elements[CAP_STATUS_IDX].integer.value;
> +       elem = out_obj->package.elements;
> +
> +       cap_hdr->status = elem[CAP_STATUS_IDX].integer.value;
>         if (cap_hdr->status != DSM_SUCCEED) {
>                 ret = -EBUSY;
>                 dev_dbg(pfru_dev->parent_dev, "Query cap Error Status:%d\n",
> @@ -158,29 +160,30 @@ static int query_capability(struct pfru_update_cap_info *cap_hdr,
>                 goto free_acpi_buffer;
>         }
>
> -       cap_hdr->update_cap = out_obj->package.elements[CAP_UPDATE_IDX].integer.value;
> +       if (elem[CAP_CODE_TYPE_IDX].buffer.length > sizeof(cap_hdr->code_type) ||
> +           elem[CAP_DRV_TYPE_IDX].buffer.length > sizeof(cap_hdr->drv_type) ||
> +           elem[CAP_PLAT_ID_IDX].buffer.length > sizeof(cap_hdr->platform_id) ||
> +           elem[CAP_OEM_ID_IDX].buffer.length > sizeof(cap_hdr->oem_id))
> +               goto free_acpi_buffer;
> +
> +       cap_hdr->update_cap = elem[CAP_UPDATE_IDX].integer.value;
>         memcpy(&cap_hdr->code_type,
> -              out_obj->package.elements[CAP_CODE_TYPE_IDX].buffer.pointer,
> -              out_obj->package.elements[CAP_CODE_TYPE_IDX].buffer.length);
> -       cap_hdr->fw_version =
> -               out_obj->package.elements[CAP_FW_VER_IDX].integer.value;
> -       cap_hdr->code_rt_version =
> -               out_obj->package.elements[CAP_CODE_RT_VER_IDX].integer.value;
> +              elem[CAP_CODE_TYPE_IDX].buffer.pointer,
> +              elem[CAP_CODE_TYPE_IDX].buffer.length);
> +       cap_hdr->fw_version = elem[CAP_FW_VER_IDX].integer.value;
> +       cap_hdr->code_rt_version = elem[CAP_CODE_RT_VER_IDX].integer.value;
>         memcpy(&cap_hdr->drv_type,
> -              out_obj->package.elements[CAP_DRV_TYPE_IDX].buffer.pointer,
> -              out_obj->package.elements[CAP_DRV_TYPE_IDX].buffer.length);
> -       cap_hdr->drv_rt_version =
> -               out_obj->package.elements[CAP_DRV_RT_VER_IDX].integer.value;
> -       cap_hdr->drv_svn =
> -               out_obj->package.elements[CAP_DRV_SVN_IDX].integer.value;
> +              elem[CAP_DRV_TYPE_IDX].buffer.pointer,
> +              elem[CAP_DRV_TYPE_IDX].buffer.length);
> +       cap_hdr->drv_rt_version = elem[CAP_DRV_RT_VER_IDX].integer.value;
> +       cap_hdr->drv_svn = elem[CAP_DRV_SVN_IDX].integer.value;
>         memcpy(&cap_hdr->platform_id,
> -              out_obj->package.elements[CAP_PLAT_ID_IDX].buffer.pointer,
> -              out_obj->package.elements[CAP_PLAT_ID_IDX].buffer.length);
> +              elem[CAP_PLAT_ID_IDX].buffer.pointer,
> +              elem[CAP_PLAT_ID_IDX].buffer.length);
>         memcpy(&cap_hdr->oem_id,
> -              out_obj->package.elements[CAP_OEM_ID_IDX].buffer.pointer,
> -              out_obj->package.elements[CAP_OEM_ID_IDX].buffer.length);
> -       cap_hdr->oem_info_len =
> -               out_obj->package.elements[CAP_OEM_INFO_IDX].buffer.length;
> +              elem[CAP_OEM_ID_IDX].buffer.pointer,
> +              elem[CAP_OEM_ID_IDX].buffer.length);
> +       cap_hdr->oem_info_len = elem[CAP_OEM_INFO_IDX].buffer.length;
>
>         ret = 0;
>
> --
> 2.55.0
>