drm/amdgpu: Check if fd really is an amdgpu fd.

Otherwise we interpret the file private data as drm & amdgpu data
while it might not be, possibly allowing one to get memory corruption.

Signed-off-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
index 7f3aa7b7e1d8..637f927e3675 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
@@ -1178,6 +1178,22 @@ static const struct file_operations amdgpu_driver_kms_fops = {
 #endif
 };
 
+int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv)
+{
+        struct drm_file *file;
+
+        if (!filp)
+                return -EINVAL;
+
+        if (filp->f_op != &amdgpu_driver_kms_fops) {
+                return -EINVAL;
+        }
+
+        file = filp->private_data;
+        *fpriv = file->driver_priv;
+        return 0;
+}
+
 static bool
 amdgpu_get_crtc_scanout_position(struct drm_device *dev, unsigned int pipe,
                                  bool in_vblank_irq, int *vpos, int *hpos,