[PATCH 6.1.y] drm/amd/pm: fix pptable use-after-free

[Sasha Levin <sashal@kernel.org>]

From: Yang Wang <kevinyang.wang@amd.com>

[ Upstream commit bb493058c35c8676e48269ab6732688ea733d23c ]

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
[ kept 6.18's existing `if (!pp_funcs->get_pp_table) return 0;` guard instead of upstream's SR-IOV/SCPM `-EOPNOTSUPP` guard and dropped the `default_attr_update()` hunk whose `pp_table` branch doesn't exist yet ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/amd/pm/amdgpu_dpm.c     | 15 +++++++++++++--
 drivers/gpu/drm/amd/pm/amdgpu_pm.c      |  8 +-------
 drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h |  3 ++-
 3 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/amdgpu_dpm.c b/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
index 69b51612c39a5..77dda3239c21c 100644
--- a/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
+++ b/drivers/gpu/drm/amd/pm/amdgpu_dpm.c
@@ -950,17 +950,28 @@ 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 && size) || (table && !size))
+		return -EINVAL;
+
 	if (!pp_funcs->get_pp_table)
 		return 0;
 
 	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 cdb406690b7e7..229049f21a89b 100644
--- a/drivers/gpu/drm/amd/pm/amdgpu_pm.c
+++ b/drivers/gpu/drm/amd/pm/amdgpu_pm.c
@@ -532,7 +532,6 @@ 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;
 
 	if (amdgpu_in_reset(adev))
@@ -546,7 +545,7 @@ static ssize_t amdgpu_get_pp_table(struct device *dev,
 		return ret;
 	}
 
-	size = amdgpu_dpm_get_pp_table(adev, &table);
+	size = amdgpu_dpm_get_pp_table(adev, buf, PAGE_SIZE - 1);
 
 	pm_runtime_mark_last_busy(ddev->dev);
 	pm_runtime_put_autosuspend(ddev->dev);
@@ -554,11 +553,6 @@ static ssize_t amdgpu_get_pp_table(struct device *dev,
 	if (size <= 0)
 		return size;
 
-	if (size >= PAGE_SIZE)
-		size = PAGE_SIZE - 1;
-
-	memcpy(buf, table, size);
-
 	return size;
 }
 
diff --git a/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h b/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h
index 338fce249f5ab..a97c27ae9702c 100644
--- a/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h
+++ b/drivers/gpu/drm/amd/pm/inc/amdgpu_dpm.h
@@ -459,7 +459,8 @@ 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,
-- 
2.53.0