From f6a3f2456d694db0f78b8cb87a816e71bf6cddf8 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Sun, 14 Nov 2021 19:29:54 +0100
Subject: [PATCH] Inherit only specific handles on Windows

To be able to communicate with a child process via stdin, stdout and
stderr, the CreateProcess() parameter bInheritHandles must be set to
TRUE. But this causes *all* handles to be inherited, including sockets.

As a result, the server socket is inherited by the process running adb
to execute the server on the device, so it may not be closed properly,
causing other scrcpy instances to fail.

To fix the issue, use an extended API to explicitly set the HANDLE to
inherit:
 - <https://stackoverflow.com/a/28185363/1987178>
 - <https://devblogs.microsoft.com/oldnewthing/20111216-00/?p=8873>

Fixes #2779 <https://github.com/Genymobile/scrcpy/issues/2779>
---
 app/src/sys/win/process.c | 88 +++++++++++++++++++++++++++++++++------
 1 file changed, 76 insertions(+), 12 deletions(-)

diff --git a/app/src/sys/win/process.c b/app/src/sys/win/process.c
index 45980790c4..6566b80e94 100644
--- a/app/src/sys/win/process.c
+++ b/app/src/sys/win/process.c
@@ -1,5 +1,10 @@
+// <https://devblogs.microsoft.com/oldnewthing/20111216-00/?p=8873>
+#define _WIN32_WINNT 0x0600 // For extended process API
+
 #include "util/process.h"
 
+#include <processthreadsapi.h>
+
 #include <assert.h>
 
 #include "util/log.h"
@@ -26,6 +31,9 @@ sc_process_execute_p(const char *const argv[], HANDLE *handle,
                      HANDLE *pin, HANDLE *pout, HANDLE *perr) {
     enum sc_process_result ret = SC_PROCESS_ERROR_GENERIC;
 
+    // Add 1 per non-NULL pointer
+    unsigned handle_count = !!pin + !!pout + !!perr;
+
     SECURITY_ATTRIBUTES sa;
     sa.nLength = sizeof(SECURITY_ATTRIBUTES);
     sa.lpSecurityDescriptor = NULL;
@@ -65,43 +73,94 @@ sc_process_execute_p(const char *const argv[], HANDLE *handle,
         }
     }
 
-    STARTUPINFOW si;
+    STARTUPINFOEXW si;
     PROCESS_INFORMATION pi;
     memset(&si, 0, sizeof(si));
-    si.cb = sizeof(si);
-    if (pin || pout || perr) {
-        si.dwFlags = STARTF_USESTDHANDLES;
+    si.StartupInfo.cb = sizeof(si);
+    HANDLE handles[3];
+
+    LPPROC_THREAD_ATTRIBUTE_LIST lpAttributeList = NULL;
+    if (handle_count) {
+        si.StartupInfo.dwFlags = STARTF_USESTDHANDLES;
         if (pin) {
-            si.hStdInput = stdin_read_handle;
+            si.StartupInfo.hStdInput = stdin_read_handle;
         }
         if (pout) {
-            si.hStdOutput = stdout_write_handle;
+            si.StartupInfo.hStdOutput = stdout_write_handle;
         }
         if (perr) {
-            si.hStdError = stderr_write_handle;
+            si.StartupInfo.hStdError = stderr_write_handle;
+        }
+
+        SIZE_T size;
+        // Call it once to know the required buffer size
+        BOOL ok =
+            InitializeProcThreadAttributeList(NULL, 1, 0, &size)
+                || GetLastError() == ERROR_INSUFFICIENT_BUFFER;
+        if (!ok) {
+            goto error_close_stderr;
+        }
+
+        lpAttributeList = malloc(size);
+        if (!lpAttributeList) {
+            goto error_close_stderr;
+        }
+
+        ok = InitializeProcThreadAttributeList(lpAttributeList, 1, 0, &size);
+        if (!ok) {
+            free(lpAttributeList);
+            goto error_close_stderr;
         }
+
+        // Explicitly pass the HANDLEs that must be inherited
+        unsigned i = 0;
+        if (pin) {
+            handles[i++] = stdin_read_handle;
+        }
+        if (pout) {
+            handles[i++] = stdout_write_handle;
+        }
+        if (perr) {
+            handles[i++] = stderr_write_handle;
+        }
+        ok = UpdateProcThreadAttribute(lpAttributeList, 0,
+                                       PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
+                                       handles, handle_count * sizeof(HANDLE),
+                                       NULL, NULL);
+        if (!ok) {
+            goto error_free_attribute_list;
+        }
+
+        si.lpAttributeList = lpAttributeList;
     }
 
     char *cmd = malloc(CMD_MAX_LEN);
     if (!cmd || !build_cmd(cmd, CMD_MAX_LEN, argv)) {
-        goto error_close_stderr;
+        goto error_free_attribute_list;
     }
 
     wchar_t *wide = sc_str_to_wchars(cmd);
     free(cmd);
     if (!wide) {
         LOGC("Could not allocate wide char string");
-        goto error_close_stderr;
+        goto error_free_attribute_list;
     }
 
-    BOOL ok = CreateProcessW(NULL, wide, NULL, NULL, TRUE, 0, NULL, NULL, &si,
-                             &pi);
+    BOOL bInheritHandles = handle_count > 0;
+    DWORD dwCreationFlags = handle_count > 0 ? EXTENDED_STARTUPINFO_PRESENT : 0;
+    BOOL ok = CreateProcessW(NULL, wide, NULL, NULL, bInheritHandles,
+                             dwCreationFlags, NULL, NULL, &si.StartupInfo, &pi);
     free(wide);
     if (!ok) {
         if (GetLastError() == ERROR_FILE_NOT_FOUND) {
             ret = SC_PROCESS_ERROR_MISSING_BINARY;
         }
-        goto error_close_stderr;
+        goto error_free_attribute_list;
+    }
+
+    if (lpAttributeList) {
+        DeleteProcThreadAttributeList(lpAttributeList);
+        free(lpAttributeList);
     }
 
     // These handles are used by the child process, close them for this process
@@ -119,6 +178,11 @@ sc_process_execute_p(const char *const argv[], HANDLE *handle,
 
     return SC_PROCESS_SUCCESS;
 
+error_free_attribute_list:
+    if (lpAttributeList) {
+        DeleteProcThreadAttributeList(lpAttributeList);
+        free(lpAttributeList);
+    }
 error_close_stderr:
     if (perr) {
         CloseHandle(*perr);