Catch integer overflows when computing the required array and mip cou…

…nts.

wgpu-core/src/device/mod.rs

@@ -948,8 +948,23 @@ impl<A: HalApi> Device<A> {
             },
         };
 
-        let required_level_count =
-            desc.range.base_mip_level + desc.range.mip_level_count.map_or(1, |count| count.get());
+        // Compute the required mip count avoiding overflow.
+        let mip_level_count = desc.range.mip_level_count.map_or(1, |count| count.get());
+        let base_mip = desc.range.base_mip_level;
+        let required_level_count = if std::u32::MAX - base_mip > mip_level_count  {
+            base_mip + mip_level_count
+        } else {
+            std::u32::MAX
+        };
+
+        let level_end = texture.full_range.mips.end;
+        if required_level_count > level_end {
+            return Err(resource::CreateTextureViewError::TooManyMipLevels {
+                requested: required_level_count,
+                total: level_end,
+            });
+        };
+
         let array_layer_count = match desc.range.array_layer_count {
             Some(count) => count.get(),
             None => match view_dim {
@@ -960,16 +975,16 @@ impl<A: HalApi> Device<A> {
                 _ => texture.desc.array_layer_count(),
             },
         };
-        let required_layer_count = array_layer_count + desc.range.base_array_layer;
 
-        let level_end = texture.full_range.mips.end;
+        // Compute the required layer count avoiding overflow.
+        let base_layer = desc.range.base_array_layer;
+        let required_layer_count = if std::u32::MAX - base_layer > array_layer_count  {
+            base_layer + array_layer_count
+        } else {
+            std::u32::MAX
+        };
+
         let layer_end = texture.full_range.layers.end;
-        if required_level_count > level_end {
-            return Err(resource::CreateTextureViewError::TooManyMipLevels {
-                requested: required_level_count,
-                total: level_end,
-            });
-        }
         if required_layer_count > layer_end {
             return Err(resource::CreateTextureViewError::TooManyArrayLayers {
                 requested: required_layer_count,