From 8903f2cc0bcade7cc296cc7518e6c0a2bf4d3e1c Mon Sep 17 00:00:00 2001
From: Stephen White <[email protected]>
Date: Tue, 09 Jun 2026 16:17:16 -0400
Subject: [PATCH] Modify validation of depth/stencil feedback loops

Allow depth/stencil read-only feedback loops on non-WebGL contexts.

Bug: angleproject:521861813
Bug: chromium:517307966
Change-Id: Ie6a3cc7460d59541941d30ff8a4d270fa26b9ead
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/7914428
Commit-Queue: Stephen White <[email protected]>
Reviewed-by: Geoff Lang <[email protected]>
Reviewed-by: Charlie Lao <[email protected]>
Reviewed-by: Shahbaz Youssefi <[email protected]>
---

diff --git a/src/libANGLE/Framebuffer.cpp b/src/libANGLE/Framebuffer.cpp
index 035383f..bb18831 100644
--- a/src/libANGLE/Framebuffer.cpp
+++ b/src/libANGLE/Framebuffer.cpp
@@ -2380,7 +2380,8 @@
     }
 }
 
-bool Framebuffer::formsRenderingFeedbackLoopWith(const Context *context) const
+bool Framebuffer::formsRenderingFeedbackLoopWith(const Context *context,
+                                                 AllowedFeedbackLoop allowedFeedbackLoop) const
 {
     const State &glState                = context->getState();
     const ProgramExecutable *executable = glState.getLinkedProgramExecutable(context);
@@ -2415,12 +2416,22 @@
 
             if (AttachmentOverlapsWithTexture(mState.mDepthAttachment, texture, sampler))
             {
-                return true;
+                if (allowedFeedbackLoop != AllowedFeedbackLoop::ReadOnlyDepthStencil ||
+                    (glState.isDepthWriteEnabled() && !texture->getState().isStencilMode()))
+                {
+                    return true;
+                }
             }
 
             if (AttachmentOverlapsWithTexture(mState.mStencilAttachment, texture, sampler))
             {
-                return true;
+                if (allowedFeedbackLoop != AllowedFeedbackLoop::ReadOnlyDepthStencil ||
+                    (glState.isStencilWriteEnabled(
+                         glState.getDrawFramebuffer()->getStencilBitCount()) &&
+                     texture->getState().isStencilMode()))
+                {
+                    return true;
+                }
             }
 
             if (pls != nullptr)
diff --git a/src/libANGLE/Framebuffer.h b/src/libANGLE/Framebuffer.h
index 555000a..74c5664 100644
--- a/src/libANGLE/Framebuffer.h
+++ b/src/libANGLE/Framebuffer.h
@@ -456,7 +456,14 @@
     // Observer implementation
     void onSubjectStateChange(angle::SubjectIndex index, angle::SubjectMessage message) override;
 
-    bool formsRenderingFeedbackLoopWith(const Context *context) const;
+    enum class AllowedFeedbackLoop : bool
+    {
+        NoneAllowed,
+        ReadOnlyDepthStencil,
+    };
+
+    bool formsRenderingFeedbackLoopWith(const Context *context,
+                                        AllowedFeedbackLoop allowedFeedbackLoop) const;
     bool formsCopyingFeedbackLoopWith(TextureID destTextureId,
                                       const gl::ImageIndex &destImageIndex) const;
 
diff --git a/src/libANGLE/validationES.cpp b/src/libANGLE/validationES.cpp
index 73761f1..5ecde1f 100644
--- a/src/libANGLE/validationES.cpp
+++ b/src/libANGLE/validationES.cpp
@@ -4245,7 +4245,10 @@
         if (ANGLE_UNLIKELY(context->isWebGL() || context->isHardenedContext()))
         {
             // UB: Detect rendering feedback loops for WebGL or hardened context.
-            if (framebuffer->formsRenderingFeedbackLoopWith(context))
+            if (framebuffer->formsRenderingFeedbackLoopWith(
+                    context, context->isWebGL()
+                                 ? Framebuffer::AllowedFeedbackLoop::NoneAllowed
+                                 : Framebuffer::AllowedFeedbackLoop::ReadOnlyDepthStencil))
             {
                 return kFeedbackLoop;
             }
diff --git a/src/tests/angle_end2end_tests_expectations.txt b/src/tests/angle_end2end_tests_expectations.txt
index 4cff1cb4..fc14680 100644
--- a/src/tests/angle_end2end_tests_expectations.txt
+++ b/src/tests/angle_end2end_tests_expectations.txt
@@ -103,6 +103,14 @@
 
 500721361 VULKAN SWIFTSHADER : VertexAttributeTestES3.storeStaticAttribWithLargeOffset/* = SKIP
 
+// Causes a write-after-write hazard on Linux/Vk
+524405499 VULKAN : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyStencil8/* = SKIP
+524405499 VULKAN : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyANGLE/* = SKIP
+
+// Asserts on Win/D3D11
+524406308 WIN D3D11 : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyStencil8/* = SKIP
+524406308 WIN D3D11 : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyANGLE/* = SKIP
+
 // Windows
 42262429 WIN NVIDIA D3D11 : BufferDataOverflowTest.VertexBufferIntegerOverflow/* = SKIP
 40096654 WIN VULKAN : BufferDataOverflowTest.VertexBufferIntegerOverflow/* = SKIP
diff --git a/src/tests/gl_tests/WebGLCompatibilityTest.cpp b/src/tests/gl_tests/WebGLCompatibilityTest.cpp
index 04f9929..8c94044 100644
--- a/src/tests/gl_tests/WebGLCompatibilityTest.cpp
+++ b/src/tests/gl_tests/WebGLCompatibilityTest.cpp
@@ -4770,6 +4770,235 @@
     EXPECT_GL_ERROR(GL_INVALID_OPERATION) << "Stencil test disabled should still fail";
 }
 
+// This test covers detection of rendering feedback loops between the FBO and a depth Texture.
+// Read-only depth/stencil feedback loops are allowed in hardened contexts and
+// should not generate an error.
+TEST_P(HardenedContextTest, RenderingFeedbackLoopWithDepthStencil)
+{
+    constexpr char kVS[] =
+        R"(#version 300 es
+in vec4 aPosition;
+out vec2 texCoord;
+void main() {
+    gl_Position = aPosition;
+    texCoord = (aPosition.xy * 0.5) + 0.5;
+})";
+
+    constexpr char kFS[] =
+        R"(#version 300 es
+precision mediump float;
+uniform sampler2D tex;
+in vec2 texCoord;
+out vec4 oColor;
+void main() {
+    oColor = texture(tex, texCoord);
+})";
+
+    GLsizei width  = 8;
+    GLsizei height = 8;
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+    glUseProgram(program);
+
+    glViewport(0, 0, width, height);
+
+    GLint texLoc = glGetUniformLocation(program, "tex");
+    glUniform1i(texLoc, 0);
+
+    // Create textures and allocate storage
+    GLTexture tex0;
+    GLTexture tex1;
+    FillTexture2D(tex0, width, height, GLColor::black, 0, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE);
+    FillTexture2D(tex1, width, height, 0x80, 0, GL_DEPTH_COMPONENT16, GL_DEPTH_COMPONENT,
+                  GL_UNSIGNED_INT);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer fbo;
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex0, 0);
+
+    // Test rendering and sampling feedback loop for depth buffer
+    glBindTexture(GL_TEXTURE_2D, tex1);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, tex1, 0);
+    ASSERT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    // The same image is used as depth buffer during rendering.
+    // This should be an error in hardened contexts.
+    glEnable(GL_DEPTH_TEST);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION) << "Same image as depth buffer should fail";
+
+    // The same image is used as depth buffer. But depth mask is false.
+    glDepthMask(GL_FALSE);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+
+    // The same image is used as depth buffer. But depth test is not enabled during rendering.
+    glDepthMask(GL_TRUE);
+    glDisable(GL_DEPTH_TEST);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+}
+
+// This test covers detection of rendering feedback loops between the FBO and a stencil texture with
+// GL_OES_texture_stencil8. Read-only stencil feedback loops are allowed in hardened contexts and
+// should not generate an error.
+TEST_P(HardenedContextTest, RenderingFeedbackLoopWithStencilOnlyStencil8)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_OES_texture_stencil8"));
+
+    constexpr char kVS[] =
+        R"(#version 300 es
+in vec4 aPosition;
+out vec2 texCoord;

diff --git a/src/tests/angle_end2end_tests_expectations.txt b/src/tests/angle_end2end_tests_expectations.txt
index 4cff1cb4..fc14680 100644
--- a/src/tests/angle_end2end_tests_expectations.txt
+++ b/src/tests/angle_end2end_tests_expectations.txt
@@ -103,6 +103,14 @@
 
 500721361 VULKAN SWIFTSHADER : VertexAttributeTestES3.storeStaticAttribWithLargeOffset/* = SKIP
 
+// Causes a write-after-write hazard on Linux/Vk
+524405499 VULKAN : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyStencil8/* = SKIP
+524405499 VULKAN : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyANGLE/* = SKIP
+
+// Asserts on Win/D3D11
+524406308 WIN D3D11 : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyStencil8/* = SKIP
+524406308 WIN D3D11 : HardenedContextTest.RenderingFeedbackLoopWithStencilOnlyANGLE/* = SKIP
+
 // Windows
 42262429 WIN NVIDIA D3D11 : BufferDataOverflowTest.VertexBufferIntegerOverflow/* = SKIP
 40096654 WIN VULKAN : BufferDataOverflowTest.VertexBufferIntegerOverflow/* = SKIP
diff --git a/src/tests/gl_tests/WebGLCompatibilityTest.cpp b/src/tests/gl_tests/WebGLCompatibilityTest.cpp
index 04f9929..8c94044 100644
--- a/src/tests/gl_tests/WebGLCompatibilityTest.cpp
+++ b/src/tests/gl_tests/WebGLCompatibilityTest.cpp
@@ -4770,6 +4770,235 @@
     EXPECT_GL_ERROR(GL_INVALID_OPERATION) << "Stencil test disabled should still fail";
 }
 
+// This test covers detection of rendering feedback loops between the FBO and a depth Texture.
+// Read-only depth/stencil feedback loops are allowed in hardened contexts and
+// should not generate an error.
+TEST_P(HardenedContextTest, RenderingFeedbackLoopWithDepthStencil)
+{
+    constexpr char kVS[] =
+        R"(#version 300 es
+in vec4 aPosition;
+out vec2 texCoord;
+void main() {
+    gl_Position = aPosition;
+    texCoord = (aPosition.xy * 0.5) + 0.5;
+})";
+
+    constexpr char kFS[] =
+        R"(#version 300 es
+precision mediump float;
+uniform sampler2D tex;
+in vec2 texCoord;
+out vec4 oColor;
+void main() {
+    oColor = texture(tex, texCoord);
+})";
+
+    GLsizei width  = 8;
+    GLsizei height = 8;
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+    glUseProgram(program);
+
+    glViewport(0, 0, width, height);
+
+    GLint texLoc = glGetUniformLocation(program, "tex");
+    glUniform1i(texLoc, 0);
+
+    // Create textures and allocate storage
+    GLTexture tex0;
+    GLTexture tex1;
+    FillTexture2D(tex0, width, height, GLColor::black, 0, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE);
+    FillTexture2D(tex1, width, height, 0x80, 0, GL_DEPTH_COMPONENT16, GL_DEPTH_COMPONENT,
+                  GL_UNSIGNED_INT);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer fbo;
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex0, 0);
+
+    // Test rendering and sampling feedback loop for depth buffer
+    glBindTexture(GL_TEXTURE_2D, tex1);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, tex1, 0);
+    ASSERT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    // The same image is used as depth buffer during rendering.
+    // This should be an error in hardened contexts.
+    glEnable(GL_DEPTH_TEST);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION) << "Same image as depth buffer should fail";
+
+    // The same image is used as depth buffer. But depth mask is false.
+    glDepthMask(GL_FALSE);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+
+    // The same image is used as depth buffer. But depth test is not enabled during rendering.
+    glDepthMask(GL_TRUE);
+    glDisable(GL_DEPTH_TEST);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+}
+
+// This test covers detection of rendering feedback loops between the FBO and a stencil texture with
+// GL_OES_texture_stencil8. Read-only stencil feedback loops are allowed in hardened contexts and
+// should not generate an error.
+TEST_P(HardenedContextTest, RenderingFeedbackLoopWithStencilOnlyStencil8)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_OES_texture_stencil8"));
+
+    constexpr char kVS[] =
+        R"(#version 300 es
+in vec4 aPosition;
+out vec2 texCoord;
+void main() {
+    gl_Position = aPosition;
+    texCoord = (aPosition.xy * 0.5) + 0.5;
+})";
+
+    constexpr char kFS[] =
+        R"(#version 300 es
+precision mediump float;
+precision mediump usampler2D;
+uniform usampler2D tex;
+in vec2 texCoord;
+out vec4 oColor;
+void main() {
+    oColor = vec4(texture(tex, texCoord)) / 256.0;
+})";
+
+    GLsizei width  = 8;
+    GLsizei height = 8;
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+    glUseProgram(program);
+
+    glViewport(0, 0, width, height);
+
+    GLint texLoc = glGetUniformLocation(program, "tex");
+    glUniform1i(texLoc, 0);
+
+    // Create textures and allocate storage
+    GLTexture tex0;
+    GLTexture tex1;
+    FillTexture2D(tex0, width, height, GLColor::black, 0, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE);
+    FillTexture2D(tex1, width, height, 0x40, 0, GL_STENCIL_INDEX8, GL_STENCIL_INDEX,
+                  GL_UNSIGNED_BYTE);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer fbo;
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex0, 0);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_TEXTURE_2D, tex1, 0);
+    ASSERT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    glBindTexture(GL_TEXTURE_2D, tex1);
+
+    // The same image is used as stencil buffer during rendering.
+    // Ensure that the stencil func and op are not no-ops, so that there can
+    // be stencil writes.
+    glEnable(GL_STENCIL_TEST);
+    glStencilFunc(GL_GREATER, 0x0000, 0xFFFFFFFF);
+    glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION) << "Same image as stencil buffer should fail";
+
+    // The same image is used as stencil buffer. But stencil mask is zero.
+    glStencilMask(0x0);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+
+    // The same image is used as stencil buffer. But stencil test is not enabled during rendering.
+    glStencilMask(0xffff);
+    glDisable(GL_STENCIL_TEST);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+}
+
+// This test covers detection of rendering feedback loops between the FBO and a stencil texture with
+// GL_ANGLE_stencil_texturing. Read-only stencil feedback loops are allowed in hardened contexts and
+// should not generate an error.
+TEST_P(HardenedContextTest, RenderingFeedbackLoopWithStencilOnlyANGLE)
+{
+    ANGLE_SKIP_TEST_IF(!EnsureGLExtensionEnabled("GL_ANGLE_stencil_texturing"));
+
+    constexpr char kVS[] =
+        R"(#version 300 es
+in vec4 aPosition;
+out vec2 texCoord;
+void main() {
+    gl_Position = aPosition;
+    texCoord = (aPosition.xy * 0.5) + 0.5;
+})";
+
+    constexpr char kFS[] =
+        R"(#version 300 es
+precision mediump float;
+precision mediump usampler2D;
+uniform usampler2D tex;
+in vec2 texCoord;
+out vec4 oColor;
+void main() {
+    oColor = vec4(texture(tex, texCoord)) / 256.0;
+})";
+
+    GLsizei width  = 8;
+    GLsizei height = 8;
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+    glUseProgram(program);
+
+    glViewport(0, 0, width, height);
+
+    GLint texLoc = glGetUniformLocation(program, "tex");
+    glUniform1i(texLoc, 0);
+
+    // Create textures and allocate storage
+    GLTexture tex0;
+    GLTexture tex1;
+    FillTexture2D(tex0, width, height, GLColor::black, 0, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE);
+    FillTexture2D(tex1, width, height, 0x40, 0, GL_DEPTH24_STENCIL8, GL_DEPTH_STENCIL,
+                  GL_UNSIGNED_INT_24_8);
+    ASSERT_GL_NO_ERROR();
+
+    GLFramebuffer fbo;
+    glBindFramebuffer(GL_FRAMEBUFFER, fbo);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, tex0, 0);
+    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_TEXTURE_2D, tex1, 0);
+    ASSERT_GL_FRAMEBUFFER_COMPLETE(GL_FRAMEBUFFER);
+
+    glBindTexture(GL_TEXTURE_2D, tex1);
+    glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_STENCIL_TEXTURE_MODE, GL_STENCIL_INDEX);
+
+    // The same image is used as stencil buffer during rendering.
+    // Ensure that the stencil func and op are not no-ops, so that there can
+    // be stencil writes.
+    glEnable(GL_STENCIL_TEST);
+    glStencilFunc(GL_GREATER, 0x0000, 0xFFFFFFFF);
+    glStencilOp(GL_KEEP, GL_REPLACE, GL_REPLACE);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_ERROR(GL_INVALID_OPERATION) << "Same image as stencil buffer should fail";
+
+    // The same image is used as stencil buffer. But stencil mask is zero.
+    glStencilMask(0x0);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+
+    // The same image is used as stencil buffer. But stencil test is not enabled during rendering.
+    glStencilMask(0xffff);
+    glDisable(GL_STENCIL_TEST);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+
+    // The same image is used as stencil buffer. But only the depth component of the texture is
+    // being read.
+    glStencilMask(0xffff);
+    glEnable(GL_STENCIL_TEST);
+    glTexParameteri(GL_TEXTURE_2D, GL_DEPTH_STENCIL_TEXTURE_MODE, GL_DEPTH_COMPONENT);
+    drawQuad(program, "aPosition", 0.5f, 1.0f, true);
+    EXPECT_GL_NO_ERROR();
+}
+
 // The source and the target for CopyTexSubImage3D are the same 3D texture.
 // But the level of the 3D texture != the level of the read attachment.
 TEST_P(WebGL2CompatibilityTest, NoTextureCopyingFeedbackLoopBetween3DLevels)