SDL: Fix buffer-overflow access in process_testStdinToStdout

SDL Commits
1 
From 32c19b9dc8c229e239434fedc94541c6abb3f84a Mon Sep 17 00:00:00 2001
From: Anonymous Maarten <[EMAIL REDACTED]>
Date: Mon, 25 May 2026 14:16:01 +0200
Subject: [PATCH] Fix buffer-overflow access in process_testStdinToStdout

Backing memory of SDL_IOFromDynamicMem is not null-terminated.
---
 test/testprocess.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test/testprocess.c b/test/testprocess.c
index d21a42a6aa886..3fa56d0376b98 100644
--- a/test/testprocess.c
+++ b/test/testprocess.c
@@ -500,7 +500,8 @@ static int process_testStdinToStdout(void *arg)
             total_read += amount_read;
             SDL_WriteIO(stdout_stream, local_buffer, amount_read);
             stdout_stream_buf = SDL_GetPointerProperty(SDL_GetIOProperties(stdout_stream), SDL_PROP_IOSTREAM_DYNAMIC_MEMORY_POINTER, NULL);
-            if (SDL_strstr(stdout_stream_buf, "EOF")) {
+            Sint64 stdout_size = SDL_GetIOSize(stdout_stream);
+            if (SDL_strnstr(stdout_stream_buf, "EOF", (size_t)stdout_size)) {
                 SDLTest_Log("Found EOF in stdout");
                 break;
             }