drm/vmwgfx: Protect from excessive execbuf kernel memory allocations v3

With the new validation code, a malicious user-space app could
potentially submit command streams with enough buffer-object and resource
references in them to have the resulting allocated validion nodes and
relocations make the kernel run out of GFP_KERNEL memory.

Protect from this by having the validation code reserve TTM graphics
memory when allocating.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Deepak Rawat <drawat@vmware.com>
---
v2: Removed leftover debug printouts

1 files changed, 36 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
index 7b1e5a5cbd2c..f88247046721 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
@@ -96,3 +96,39 @@ void vmw_ttm_global_release(struct vmw_private *dev_priv)
 	drm_global_item_unref(&dev_priv->bo_global_ref.ref);
 	drm_global_item_unref(&dev_priv->mem_global_ref);
 }
+
+/* struct vmw_validation_mem callback */
+static int vmw_vmt_reserve(struct vmw_validation_mem *m, size_t size)
+{
+	static struct ttm_operation_ctx ctx = {.interruptible = false,
+					       .no_wait_gpu = false};
+	struct vmw_private *dev_priv = container_of(m, struct vmw_private, vvm);
+
+	return ttm_mem_global_alloc(vmw_mem_glob(dev_priv), size, &ctx);
+}
+
+/* struct vmw_validation_mem callback */
+static void vmw_vmt_unreserve(struct vmw_validation_mem *m, size_t size)
+{
+	struct vmw_private *dev_priv = container_of(m, struct vmw_private, vvm);
+
+	return ttm_mem_global_free(vmw_mem_glob(dev_priv), size);
+}
+
+/**
+ * vmw_validation_mem_init_ttm - Interface the validation memory tracker
+ * to ttm.
+ * @dev_priv: Pointer to struct vmw_private. The reason we choose a vmw private
+ * rather than a struct vmw_validation_mem is to make sure assumption in the
+ * callbacks that struct vmw_private derives from struct vmw_validation_mem
+ * holds true.
+ * @gran: The recommended allocation granularity
+ */
+void vmw_validation_mem_init_ttm(struct vmw_private *dev_priv, size_t gran)
+{
+	struct vmw_validation_mem *vvm = &dev_priv->vvm;
+
+	vvm->reserve_mem = vmw_vmt_reserve;
+	vvm->unreserve_mem = vmw_vmt_unreserve;
+	vvm->gran = gran;
+}