If a BIOS provides bad data in response to an ATIF method call
this causes a NULL pointer dereference in the caller.
```
? show_regs (arch/x86/kernel/dumpstack.c:478 (discriminator 1))
? __die (arch/x86/kernel/dumpstack.c:423 arch/x86/kernel/dumpstack.c:434)
? page_fault_oops (arch/x86/mm/fault.c:544 (discriminator 2) arch/x86/mm/fault.c:705 (discriminator 2))
? do_user_addr_fault (arch/x86/mm/fault.c:440 (discriminator 1) arch/x86/mm/fault.c:1232 (discriminator 1))
? acpi_ut_update_object_reference (drivers/acpi/acpica/utdelete.c:642)
? exc_page_fault (arch/x86/mm/fault.c:1542)
? asm_exc_page_fault (./arch/x86/include/asm/idtentry.h:623)
? amdgpu_atif_query_backlight_caps.constprop.0 (drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c:387 (discriminator 2)) amdgpu
? amdgpu_atif_query_backlight_caps.constprop.0 (drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c:386 (discriminator 1)) amdgpu
```
It has been encountered on at least one system, so guard for it.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)")
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index f85ace0384d2..1f5a296f5ed2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -147,6 +147,7 @@ static union acpi_object *amdgpu_atif_call(struct amdgpu_atif *atif,
struct acpi_buffer *params)
{
acpi_status status;
+ union acpi_object *obj;
union acpi_object atif_arg_elements[2];
struct acpi_object_list atif_arg;
struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
@@ -169,16 +170,24 @@ static union acpi_object *amdgpu_atif_call(struct amdgpu_atif *atif,
status = acpi_evaluate_object(atif->handle, NULL, &atif_arg,
&buffer);
+ obj = (union acpi_object *)buffer.pointer;
- /* Fail only if calling the method fails and ATIF is supported */
+ /* Fail if calling the method fails and ATIF is supported */
if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
DRM_DEBUG_DRIVER("failed to evaluate ATIF got %s\n",
acpi_format_exception(status));
- kfree(buffer.pointer);
+ kfree(obj);
return NULL;
}
- return buffer.pointer;
+ if (obj->type != ACPI_TYPE_BUFFER) {
+ DRM_DEBUG_DRIVER("bad object returned from ATIF: %d\n",
+ obj->type);
+ kfree(obj);
+ return NULL;
+ }
+
+ return obj;
}
/**
--
2.43.0
