From 0aaa69e4d73fb5ecc7f2eb2d2a2d84804704b962 Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Wed, 26 Feb 2020 16:51:53 -0300
Subject: [PATCH] vk_swapchain: Silence TOCTOU race condition
It's possible that the window is resized from the moment we ask for its
size to the moment a swapchain is created, causing validation issues.
To workaround this Vulkan issue request the capabilities again just
before creating the swapchain, making the race condition less likely.
---
.../renderer_vulkan/vk_swapchain.cpp | 21 +++++++++++--------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/src/video_core/renderer_vulkan/vk_swapchain.cpp b/src/video_core/renderer_vulkan/vk_swapchain.cpp
index f47b691a8..9e73fa9cd 100644
--- a/src/video_core/renderer_vulkan/vk_swapchain.cpp
+++ b/src/video_core/renderer_vulkan/vk_swapchain.cpp
@@ -141,11 +141,6 @@ void VKSwapchain::CreateSwapchain(const vk::SurfaceCapabilitiesKHR& capabilities
const vk::SurfaceFormatKHR surface_format{ChooseSwapSurfaceFormat(formats, srgb)};
const vk::PresentModeKHR present_mode{ChooseSwapPresentMode(present_modes)};
- extent = ChooseSwapExtent(capabilities, width, height);
-
- current_width = extent.width;
- current_height = extent.height;
- current_srgb = srgb;
u32 requested_image_count{capabilities.minImageCount + 1};
if (capabilities.maxImageCount > 0 && requested_image_count > capabilities.maxImageCount) {
@@ -153,10 +148,9 @@ void VKSwapchain::CreateSwapchain(const vk::SurfaceCapabilitiesKHR& capabilities
}
vk::SwapchainCreateInfoKHR swapchain_ci(
- {}, surface, requested_image_count, surface_format.format, surface_format.colorSpace,
- extent, 1, vk::ImageUsageFlagBits::eColorAttachment, {}, {}, {},
- capabilities.currentTransform, vk::CompositeAlphaFlagBitsKHR::eOpaque, present_mode, false,
- {});
+ {}, surface, requested_image_count, surface_format.format, surface_format.colorSpace, {}, 1,
+ vk::ImageUsageFlagBits::eColorAttachment, {}, {}, {}, capabilities.currentTransform,
+ vk::CompositeAlphaFlagBitsKHR::eOpaque, present_mode, false, {});
const u32 graphics_family{device.GetGraphicsFamily()};
const u32 present_family{device.GetPresentFamily()};
@@ -169,9 +163,18 @@ void VKSwapchain::CreateSwapchain(const vk::SurfaceCapabilitiesKHR& capabilities
swapchain_ci.imageSharingMode = vk::SharingMode::eExclusive;
}
+ // Request the size again to reduce the possibility of a TOCTOU race condition.
+ const auto updated_capabilities = physical_device.getSurfaceCapabilitiesKHR(surface, dld);
+ swapchain_ci.imageExtent = ChooseSwapExtent(updated_capabilities, width, height);
+ // Don't add code within this and the swapchain creation.
const auto dev{device.GetLogical()};
swapchain = dev.createSwapchainKHRUnique(swapchain_ci, nullptr, dld);
+ extent = swapchain_ci.imageExtent;
+ current_width = extent.width;
+ current_height = extent.height;
+ current_srgb = srgb;
+
images = dev.getSwapchainImagesKHR(*swapchain, dld);
image_count = static_cast<u32>(images.size());
image_format = surface_format.format;