drm/exynos: iommu: move dma_params configuration code to separate functions

Move code for managing DMA max segment size parameter to separate
functions. This patch also replaces devm_kzalloc() with kzalloc() and
adds proper kfree call. devm_kzalloc() cannot be used for dma_params
structure, because it will be freed on driver remove not on device
release. This means in case of Exynos DRM being compiled as module and
loaded 2 times, a user-after-free issue will happen.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

1 files changed, 22 insertions, 6 deletions

diff --git a/drivers/gpu/drm/exynos/exynos_drm_iommu.c b/drivers/gpu/drm/exynos/exynos_drm_iommu.c
index 7ca09ee19656..1e82529e0c41 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_iommu.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_iommu.c
@@ -21,6 +21,23 @@
 #include "exynos_drm_drv.h"
 #include "exynos_drm_iommu.h"
 
+static inline int configure_dma_max_seg_size(struct device *dev)
+{
+        if (!dev->dma_parms)
+                dev->dma_parms = kzalloc(sizeof(*dev->dma_parms), GFP_KERNEL);
+        if (!dev->dma_parms)
+                return -ENOMEM;
+
+        dma_set_max_seg_size(dev, DMA_BIT_MASK(32));
+        return 0;
+}
+
+static inline void clear_dma_max_seg_size(struct device *dev)
+{
+        kfree(dev->dma_parms);
+        dev->dma_parms = NULL;
+}
+
 /*
  * drm_create_iommu_mapping - create a mapping structure
  *
@@ -80,13 +97,10 @@ int drm_iommu_attach_device(struct drm_device *drm_dev,
         if (!priv->mapping)
                 return 0;
 
-        subdrv_dev->dma_parms = devm_kzalloc(subdrv_dev,
-                                        sizeof(*subdrv_dev->dma_parms),
-                                        GFP_KERNEL);
-        if (!subdrv_dev->dma_parms)
-                return -ENOMEM;
 
-        dma_set_max_seg_size(subdrv_dev, 0xffffffffu);
+        ret = configure_dma_max_seg_size(subdrv_dev);
+        if (ret)
+                return ret;
 
         if (subdrv_dev->archdata.mapping)
                 arm_iommu_detach_device(subdrv_dev);
@@ -94,6 +108,7 @@ int drm_iommu_attach_device(struct drm_device *drm_dev,
         ret = arm_iommu_attach_device(subdrv_dev, priv->mapping);
         if (ret < 0) {
                 DRM_DEBUG_KMS("failed iommu attach.\n");
+                clear_dma_max_seg_size(subdrv_dev);
                 return ret;
         }
 
@@ -119,4 +134,5 @@ void drm_iommu_detach_device(struct drm_device *drm_dev,
                 return;
 
         arm_iommu_detach_device(subdrv_dev);
+        clear_dma_max_seg_size(subdrv_dev);
 }