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

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -49,6 +49,8 @@
 
 #define VMWGFX_REPO "In Tree"
 
+#define VMWGFX_VALIDATION_MEM_GRAN (16*PAGE_SIZE)
+
 
 /**
  * Fully encoded drm commands. Might move to vmw_drm.h
@@ -918,7 +920,7 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 		spin_unlock(&dev_priv->cap_lock);
 	}
 
-
+	vmw_validation_mem_init_ttm(dev_priv, VMWGFX_VALIDATION_MEM_GRAN);
 	ret = vmw_kms_init(dev_priv);
 	if (unlikely(ret != 0))
 		goto out_no_kms;

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -606,6 +606,9 @@ struct vmw_private {
 
 	struct vmw_cmdbuf_man *cman;
 	DECLARE_BITMAP(irqthread_pending, VMW_IRQTHREAD_MAX);
+
+	/* Validation memory reservation */
+	struct vmw_validation_mem vvm;
 };
 
 static inline struct vmw_surface *vmw_res_to_srf(struct vmw_resource *res)
@@ -846,6 +849,8 @@ extern int vmw_ttm_global_init(struct vmw_private *dev_priv);
 extern void vmw_ttm_global_release(struct vmw_private *dev_priv);
 extern int vmw_mmap(struct file *filp, struct vm_area_struct *vma);
 
+extern void vmw_validation_mem_init_ttm(struct vmw_private *dev_priv,
+					size_t gran);
 /**
  * TTM buffer object driver - vmwgfx_ttm_buffer.c
  */

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -3835,6 +3835,8 @@ int vmw_execbuf_process(struct drm_file *file_priv,
 	struct sync_file *sync_file = NULL;
 	DECLARE_VAL_CONTEXT(val_ctx, &sw_context->res_ht, 1);
 
+	vmw_validation_set_val_mem(&val_ctx, &dev_priv->vvm);
+
 	if (flags & DRM_VMW_EXECBUF_FLAG_EXPORT_FENCE_FD) {
 		out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
 		if (out_fence_fd < 0) {

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;
+}

drivers/gpu/drm/vmwgfx/vmwgfx_validation.c

@@ -104,11 +104,25 @@ void *vmw_validation_mem_alloc(struct vmw_validation_context *ctx,
 		return NULL;
 
 	if (ctx->mem_size_left < size) {
-		struct page *page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		struct page *page;
 
+		if (ctx->vm && ctx->vm_size_left < PAGE_SIZE) {
+			int ret = ctx->vm->reserve_mem(ctx->vm, ctx->vm->gran);
+
+			if (ret)
+				return NULL;
+
+			ctx->vm_size_left += ctx->vm->gran;
+			ctx->total_mem += ctx->vm->gran;
+		}
+
+		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
 		if (!page)
 			return NULL;
 
+		if (ctx->vm)
+			ctx->vm_size_left -= PAGE_SIZE;
+
 		list_add_tail(&page->lru, &ctx->page_list);
 		ctx->page_address = page_address(page);
 		ctx->mem_size_left = PAGE_SIZE;
@@ -138,6 +152,11 @@ static void vmw_validation_mem_free(struct vmw_validation_context *ctx)
 	}
 
 	ctx->mem_size_left = 0;
+	if (ctx->vm && ctx->total_mem) {
+		ctx->vm->unreserve_mem(ctx->vm, ctx->total_mem);
+		ctx->total_mem = 0;
+		ctx->vm_size_left = 0;
+	}
 }
 
 /**

drivers/gpu/drm/vmwgfx/vmwgfx_validation.h

@@ -33,6 +33,21 @@
 #include <linux/ww_mutex.h>
 #include <drm/ttm/ttm_execbuf_util.h>
 
+/**
+ * struct vmw_validation_mem - Custom interface to provide memory reservations
+ * for the validation code.
+ * @reserve_mem: Callback to reserve memory
+ * @unreserve_mem: Callback to unreserve memory
+ * @gran: Reservation granularity. Contains a hint how much memory should
+ * be reserved in each call to @reserve_mem(). A slow implementation may want
+ * reservation to be done in large batches.
+ */
+struct vmw_validation_mem {
+	int (*reserve_mem)(struct vmw_validation_mem *m, size_t size);
+	void (*unreserve_mem)(struct vmw_validation_mem *m, size_t size);
+	size_t gran;
+};
+
 /**
  * struct vmw_validation_context - Per command submission validation context
  * @ht: Hash table used to find resource- or buffer object duplicates
@@ -47,6 +62,10 @@
  * buffer objects
  * @mem_size_left: Free memory left in the last page in @page_list
  * @page_address: Kernel virtual address of the last page in @page_list
+ * @vm: A pointer to the memory reservation interface or NULL if no
+ * memory reservation is needed.
+ * @vm_size_left: Amount of reserved memory that so far has not been allocated.
+ * @total_mem: Amount of reserved memory.
  */
 struct vmw_validation_context {
 	struct drm_open_hash *ht;
@@ -59,6 +78,9 @@ struct vmw_validation_context {
 	unsigned int merge_dups;
 	unsigned int mem_size_left;
 	u8 *page_address;
+	struct vmw_validation_mem *vm;
+	size_t vm_size_left;
+	size_t total_mem;
 };
 
 struct vmw_buffer_object;
@@ -101,6 +123,21 @@ vmw_validation_has_bos(struct vmw_validation_context *ctx)
 	return !list_empty(&ctx->bo_list);
 }
 
+/**
+ * vmw_validation_set_val_mem - Register a validation mem object for
+ * validation memory reservation
+ * @ctx: The validation context
+ * @vm: Pointer to a struct vmw_validation_mem
+ *
+ * Must be set before the first attempt to allocate validation memory.
+ */
+static inline void
+vmw_validation_set_val_mem(struct vmw_validation_context *ctx,
+			   struct vmw_validation_mem *vm)
+{
+	ctx->vm = vm;
+}
+
 /**
  * vmw_validation_set_ht - Register a hash table for duplicate finding
  * @ctx: The validation context