drm/amd/pm: fix pptable use-after-free

amdgpu_dpm_get_pp_table() returns a pointer to a driver-owned power table
after dropping adev->pm.mutex. The sysfs path then copies from that pointer.
A concurrent pp_table write can replace and free the allocation during the
copy, causing a use-after-free.

Change the DPM interface to copy into caller-provided storage while the mutex
is held. Keep the size-only query for attribute discovery without exposing
the driver-owned pointer.

Fixes: 1684d3ba4885 ("drm/amd/amdgpu: change pptable output format from ASCII to binary")
Signed-off-by: Yang Wang <kevinyang.wang@amd.com>
Reviewed-by: Kenneth Feng <kenneth.feng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f6eed7acfd30099ef7baeb6ba45bb59daad80631)
Cc: stable@vger.kernel.org

3 files changed, 16 insertions, 14 deletions

diff --git a/drivers/gpu/drm/amd/pm/amdgpu_dpm.c b/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
index f76ba6753551..c787e772b3cc 100644
--- a/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
+++ b/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
@@ -1183,12 +1183,14 @@ int amdgpu_dpm_dispatch_task(struct amdgpu_device *adev,
 	return ret;
 }
 
-int amdgpu_dpm_get_pp_table(struct amdgpu_device *adev, char **table)
+int amdgpu_dpm_get_pp_table(struct amdgpu_device *adev, char *table,
+			    size_t size)
 {
 	const struct amd_pm_funcs *pp_funcs = adev->powerplay.pp_funcs;
+	char *pptable = NULL;
 	int ret = 0;
 
-	if (!table)
+	if ((!table && size) || (table && !size))
 		return -EINVAL;
 
 	if (amdgpu_sriov_vf(adev) || !pp_funcs->get_pp_table || adev->scpm_enabled)
@@ -1196,7 +1198,13 @@ int amdgpu_dpm_get_pp_table(struct amdgpu_device *adev, char **table)
 
 	mutex_lock(&adev->pm.mutex);
 	ret = pp_funcs->get_pp_table(adev->powerplay.pp_handle,
-				     table);
+				     &pptable);
+	if (ret > 0 && !pptable) {
+		ret = -EINVAL;
+	} else if (ret > 0 && table) {
+		ret = min_t(size_t, ret, size);
+		memcpy(table, pptable, ret);
+	}
 	mutex_unlock(&adev->pm.mutex);
 
 	return ret;
diff --git a/drivers/gpu/drm/amd/pm/amdgpu_pm.c b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
index 97da01aff76c..d94ea54c33c3 100644
--- a/drivers/gpu/drm/amd/pm/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
@@ -564,25 +564,19 @@ static ssize_t amdgpu_get_pp_table(struct device *dev,
 {
 	struct drm_device *ddev = dev_get_drvdata(dev);
 	struct amdgpu_device *adev = drm_to_adev(ddev);
-	char *table = NULL;
 	int size, ret;
 
 	ret = amdgpu_pm_get_access_if_active(adev);
 	if (ret)
 		return ret;
 
-	size = amdgpu_dpm_get_pp_table(adev, &table);
+	size = amdgpu_dpm_get_pp_table(adev, buf, PAGE_SIZE - 1);
 
 	amdgpu_pm_put_access(adev);
 
 	if (size <= 0)
 		return size;
 
-	if (size >= PAGE_SIZE)
-		size = PAGE_SIZE - 1;
-
-	memcpy(buf, table, size);
-
 	return size;
 }
 
@@ -2726,10 +2720,9 @@ static int default_attr_update(struct amdgpu_device *adev, struct amdgpu_device_
 			*states = ATTR_STATE_UNSUPPORTED;
 	} else if (DEVICE_ATTR_IS(pp_table)) {
 		int ret;
-		char *tmp = NULL;
 
-		ret = amdgpu_dpm_get_pp_table(adev, &tmp);
-		if (ret == -EOPNOTSUPP || !tmp)
+		ret = amdgpu_dpm_get_pp_table(adev, NULL, 0);
+		if (ret <= 0)
 			*states = ATTR_STATE_UNSUPPORTED;
 		else
 			*states = ATTR_STATE_SUPPORTED;
diff --git a/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h b/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h
index aa3f427819a0..e95cd22a31cf 100644
--- a/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h
+++ b/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h
@@ -487,7 +487,8 @@ int amdgpu_dpm_get_pp_num_states(struct amdgpu_device *adev,
 int amdgpu_dpm_dispatch_task(struct amdgpu_device *adev,
 			      enum amd_pp_task task_id,
 			      enum amd_pm_state_type *user_state);
-int amdgpu_dpm_get_pp_table(struct amdgpu_device *adev, char **table);
+int amdgpu_dpm_get_pp_table(struct amdgpu_device *adev, char *table,
+			    size_t size);
 int amdgpu_dpm_set_fine_grain_clk_vol(struct amdgpu_device *adev,
 				      uint32_t type,
 				      long *input,