Security fix on via: Checking that the specified context belongs to the

    caller on fb / agp memory alloc and free. Otherwise malicious clients
    can register allocations on other clients or free memory used by other
    clients which will lead to severe memory manager inconsistensies.

2 files changed, 31 insertions, 0 deletions

diff --git a/linux-core/drmP.h b/linux-core/drmP.h
index 2b4dbcf6..8fed5e72 100644
--- a/linux-core/drmP.h
+++ b/linux-core/drmP.h
@@ -838,6 +838,7 @@ extern int drm_context_switch_complete(drm_device_t * dev, int new);
 extern int drm_ctxbitmap_init(drm_device_t * dev);
 extern void drm_ctxbitmap_cleanup(drm_device_t * dev);
 extern void drm_ctxbitmap_free(drm_device_t * dev, int ctx_handle);
+extern int drm_check_context(drm_file_t *priv, drm_context_t handle);
 
 extern int drm_setsareactx(struct inode *inode, struct file *filp,
 			   unsigned int cmd, unsigned long arg);
diff --git a/linux-core/drm_context.c b/linux-core/drm_context.c
index baa8437d..2f947191 100644
--- a/linux-core/drm_context.c
+++ b/linux-core/drm_context.c
@@ -576,4 +576,34 @@ int drm_rmctx(struct inode *inode, struct file *filp,
 	return 0;
 }
 
+/**
+ * Check that a context is registered for a caller.
+ *
+ * \param priv file pointer private structure.
+ * \param handle context handle.
+ * \param arg user argument pointing to a drm_ctx structure.
+ * \return one if the context is registered with the file pointer. Zero otherwise.
+ */
+
+int drm_check_context(drm_file_t *priv, drm_context_t handle)
+{
+	drm_device_t *dev = priv->head->dev;
+	int ret = 0;
+
+	down(&dev->ctxlist_sem);
+	if (dev->ctxlist && !list_empty(&dev->ctxlist->head)) {
+		drm_ctx_list_t *pos, *n;
+
+		list_for_each_entry_safe(pos, n, &dev->ctxlist->head, head) {
+			if (pos->handle == handle) {
+				ret = (pos->tag == priv);
+				break;
+			}
+		}
+	}
+	up(&dev->ctxlist_sem);
+	return ret;
+}
+	
+
 /*@}*/