From 9124371e21160714b6cd6c3e7a7908676df2312f Mon Sep 17 00:00:00 2001
From: Vincent Rabaud <vrabaud@google.com>
Date: Fri, 4 Sep 2026 11:57:49 +0200
Subject: [PATCH] Fix infinite loop in warpAffine

Otherwise, p alternates between 1 and -1
That fix is already present in borderInterpolate
https://github.com/opencv/opencv/blob/3a718750a4d4bcde78bc93bcaf18b0303e956e55/modules/core/src/copy.cpp#L975
---
 modules/imgproc/src/warp_kernels.simd.hpp |  2 ++
 modules/imgproc/test/test_imgwarp.cpp     | 30 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/modules/imgproc/src/warp_kernels.simd.hpp b/modules/imgproc/src/warp_kernels.simd.hpp
index bda168095e..341462d9c7 100644
--- a/modules/imgproc/src/warp_kernels.simd.hpp
+++ b/modules/imgproc/src/warp_kernels.simd.hpp
@@ -336,6 +336,8 @@ static inline int borderInterpolate_fast( int p, int len, int borderType )
         p = p < 0 ? 0 : len - 1;
     else if( borderType == BORDER_REFLECT || borderType == BORDER_REFLECT_101 )
     {
+        if( len == 1 )
+            return 0;
         int delta = borderType == BORDER_REFLECT_101;
         do
         {
diff --git a/modules/imgproc/test/test_imgwarp.cpp b/modules/imgproc/test/test_imgwarp.cpp
index 6975c31a3b..ee3a21f18a 100644
--- a/modules/imgproc/test/test_imgwarp.cpp
+++ b/modules/imgproc/test/test_imgwarp.cpp
@@ -43,6 +43,10 @@
 #include "opencv2/ts/ts_gtest.h"
 #include "test_precomp.hpp"
 
+#include <chrono>
+#include <future>
+#include <thread>
+
 namespace opencv_test { namespace {
 
 class CV_ImgWarpBaseTest : public cvtest::ArrayTest
@@ -1199,5 +1203,31 @@ TEST(Imgproc_Warping, DISABLED_playground)
     }
 }
 
+TEST(Imgproc_Warping, infinite_loop)
+{
+    std::promise<void> promise;
+    auto future = promise.get_future();
+
+    std::thread worker([&promise]() {
+        cv::Mat src(1, 10, CV_8UC1, cv::Scalar(128));
+        cv::Mat dst;
+        cv::Matx23f M(1.f, 0.f, 0.f, 0.f, 1.f, 0.f);
+
+        cv::warpAffine(src, dst, M, cv::Size(10, 10), cv::INTER_CUBIC,
+                       cv::BORDER_REFLECT_101);
+        promise.set_value();
+    });
+
+    auto status = future.wait_for(std::chrono::seconds(1));
+    if (status == std::future_status::ready) {
+        worker.join();
+    } else {
+        worker.detach();
+    }
+
+    EXPECT_EQ(status, std::future_status::ready)
+        << "cv::warpAffine hung in an infinite loop!";
+}
+
 }} // namespace
 /* End of file. */