Sanitize Gif descriptor bounds.

src/ImageSharp/Formats/Gif/GifDecoderCore.cs

@@ -535,7 +535,8 @@ private void RestoreToBackground<TPixel>(ImageFrame<TPixel> frame)
                 return;
             }
 
-            Buffer2DRegion<TPixel> pixelRegion = frame.PixelBuffer.GetRegion(this.restoreArea.Value);
+            var interest = Rectangle.Intersect(frame.Bounds(), this.restoreArea.Value);
+            Buffer2DRegion<TPixel> pixelRegion = frame.PixelBuffer.GetRegion(interest);
             pixelRegion.Clear();
 
             this.restoreArea = null;

tests/ImageSharp.Tests/Formats/Gif/GifDecoderTests.cs

@@ -171,6 +171,17 @@ public void CanDecodeIntermingledImages()
             }
         }
 
+        // https://github.com/SixLabors/ImageSharp/issues/1503
+        [Theory]
+        [WithFile(TestImages.Gif.Issues.Issue1530, PixelTypes.Rgba32)]
+        public void Issue1530_BadDescriptorDimensions<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : unmanaged, IPixel<TPixel>
+        {
+            using Image<TPixel> image = provider.GetImage();
+            image.DebugSaveMultiFrame(provider);
+            image.CompareToReferenceOutputMultiFrame(provider, ImageComparer.Exact);
+        }
+
         // https://github.com/SixLabors/ImageSharp/issues/405
         [Theory]
         [WithFile(TestImages.Gif.Issues.BadAppExtLength, PixelTypes.Rgba32)]
@@ -181,6 +192,7 @@ public void Issue405_BadApplicationExtensionBlockLength<TPixel>(TestImageProvide
             using (Image<TPixel> image = provider.GetImage())
             {
                 image.DebugSave(provider);
+
                 image.CompareFirstFrameToReferenceOutput(ImageComparer.Exact, provider);
             }
         }

tests/ImageSharp.Tests/TestImages.cs

@@ -416,6 +416,7 @@ public static class Issues
                 public const string BadAppExtLength_2 = "Gif/issues/issue405_badappextlength252-2.gif";
                 public const string BadDescriptorWidth = "Gif/issues/issue403_baddescriptorwidth.gif";
                 public const string Issue1505 = "Gif/issues/issue1505_argumentoutofrange.png";
+                public const string Issue1530 = "Gif/issues/issue1530.gif";
             }
 
             public static readonly string[] All = { Rings, Giphy, Cheers, Trans, Kumin, Leo, Ratio4x1, Ratio1x4 };