Merge branch 'inherit-only-stdhandles'

When spawning child processes, we do want them to inherit the standard
handles so that we can talk to them. We do *not* want them to inherit
any other handle, as that would hold a lock to the respective files
(preventing them from being renamed, modified or deleted), and the child
process would not know how to access that handle anyway.

Happily, there is an API to make that happen. It is supported in Windows
Vista and later, which is exactly what we promise to support in Git for
Windows for the time being.

This also means that we lift, at long last, the target Windows version
from Windows XP to Windows Vista.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

compat/mingw.c

@@ -274,7 +274,6 @@ int mingw_core_config(const char *var, const char *value, void *cb)
 }
 
 static DWORD symlink_file_flags = 0, symlink_directory_flags = 1;
-DECLARE_PROC_ADDR(kernel32.dll, BOOLEAN, CreateSymbolicLinkW, LPCWSTR, LPCWSTR, DWORD);
 
 enum phantom_symlink_result {
 	PHANTOM_SYMLINK_RETRY,
@@ -1604,8 +1603,13 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 			      const char *dir, const char *prepend_cmd,
 			      int fhin, int fhout, int fherr)
 {
-	STARTUPINFOW si;
+	static int restrict_handle_inheritance = 1;
+	STARTUPINFOEXW si;
 	PROCESS_INFORMATION pi;
+	LPPROC_THREAD_ATTRIBUTE_LIST attr_list = NULL;
+	HANDLE stdhandles[3];
+	DWORD stdhandles_count = 0;
+	SIZE_T size;
 	struct strbuf args;
 	wchar_t wcmd[MAX_PATH], wdir[MAX_PATH], *wargs, *wenvblk = NULL;
 	unsigned flags = CREATE_UNICODE_ENVIRONMENT;
@@ -1642,11 +1646,23 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 		CloseHandle(cons);
 	}
 	memset(&si, 0, sizeof(si));
-	si.cb = sizeof(si);
-	si.dwFlags = STARTF_USESTDHANDLES;
-	si.hStdInput = winansi_get_osfhandle(fhin);
-	si.hStdOutput = winansi_get_osfhandle(fhout);
-	si.hStdError = winansi_get_osfhandle(fherr);
+	si.StartupInfo.cb = sizeof(si);
+	si.StartupInfo.hStdInput = winansi_get_osfhandle(fhin);
+	si.StartupInfo.hStdOutput = winansi_get_osfhandle(fhout);
+	si.StartupInfo.hStdError = winansi_get_osfhandle(fherr);
+
+	/* The list of handles cannot contain duplicates */
+	if (si.StartupInfo.hStdInput != INVALID_HANDLE_VALUE)
+		stdhandles[stdhandles_count++] = si.StartupInfo.hStdInput;
+	if (si.StartupInfo.hStdOutput != INVALID_HANDLE_VALUE &&
+	    si.StartupInfo.hStdOutput != si.StartupInfo.hStdInput)
+		stdhandles[stdhandles_count++] = si.StartupInfo.hStdOutput;
+	if (si.StartupInfo.hStdError != INVALID_HANDLE_VALUE &&
+	    si.StartupInfo.hStdError != si.StartupInfo.hStdInput &&
+	    si.StartupInfo.hStdError != si.StartupInfo.hStdOutput)
+		stdhandles[stdhandles_count++] = si.StartupInfo.hStdError;
+	if (stdhandles_count)
+		si.StartupInfo.dwFlags |= STARTF_USESTDHANDLES;
 
 	/* executables and the current directory don't support long paths */
 	if (*argv && !strcmp(cmd, *argv))
@@ -1705,16 +1721,97 @@ static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaen
 	wenvblk = make_environment_block(deltaenv);
 
 	memset(&pi, 0, sizeof(pi));
-	ret = CreateProcessW(*wcmd ? wcmd : NULL, wargs, NULL, NULL, TRUE,
-		flags, wenvblk, dir ? wdir : NULL, &si, &pi);
+	if (restrict_handle_inheritance && stdhandles_count &&
+	    (InitializeProcThreadAttributeList(NULL, 1, 0, &size) ||
+	     GetLastError() == ERROR_INSUFFICIENT_BUFFER) &&
+	    (attr_list = (LPPROC_THREAD_ATTRIBUTE_LIST)
+			(HeapAlloc(GetProcessHeap(), 0, size))) &&
+	    InitializeProcThreadAttributeList(attr_list, 1, 0, &size) &&
+	    UpdateProcThreadAttribute(attr_list, 0,
+				      PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
+				      stdhandles,
+				      stdhandles_count * sizeof(HANDLE),
+				      NULL, NULL)) {
+		si.lpAttributeList = attr_list;
+		flags |= EXTENDED_STARTUPINFO_PRESENT;
+	}
+
+	ret = CreateProcessW(*wcmd ? wcmd : NULL, wargs, NULL, NULL,
+			     stdhandles_count ? TRUE : FALSE,
+			     flags, wenvblk, dir ? wdir : NULL,
+			     &si.StartupInfo, &pi);
+
+	/*
+	 * On Windows 2008 R2, it seems that specifying certain types of handles
+	 * (such as FILE_TYPE_CHAR or FILE_TYPE_PIPE) will always produce an
+	 * error. Rather than playing finicky and fragile games, let's just try
+	 * to detect this situation and simply try again without restricting any
+	 * handle inheritance. This is still better than failing to create
+	 * processes.
+	 */
+	if (!ret && restrict_handle_inheritance && stdhandles_count) {
+		DWORD err = GetLastError();
+		struct strbuf buf = STRBUF_INIT;
+
+		if (err != ERROR_NO_SYSTEM_RESOURCES &&
+		    /*
+		     * On Windows 7 and earlier, handles on pipes and character
+		     * devices are inherited automatically, and cannot be
+		     * specified in the thread handle list. Rather than trying
+		     * to catch each and every corner case (and running the
+		     * chance of *still* forgetting a few), let's just fall
+		     * back to creating the process without trying to limit the
+		     * handle inheritance.
+		     */
+		    !(err == ERROR_INVALID_PARAMETER &&
+		      GetVersion() >> 16 < 9200) &&
+		    !getenv("SUPPRESS_HANDLE_INHERITANCE_WARNING")) {
+			DWORD fl = 0;
+			int i;
+
+			setenv("SUPPRESS_HANDLE_INHERITANCE_WARNING", "1", 1);
+
+			for (i = 0; i < stdhandles_count; i++) {
+				HANDLE h = stdhandles[i];
+				strbuf_addf(&buf, "handle #%d: %p (type %lx, "
+					    "handle info (%d) %lx\n", i, h,
+					    GetFileType(h),
+					    GetHandleInformation(h, &fl),
+					    fl);
+			}
+			strbuf_addstr(&buf, "\nThis is a bug; please report it "
+				      "at\nhttps://github.com/git-for-windows/"
+				      "git/issues/new\n\n"
+				      "To suppress this warning, please set "
+				      "the environment variable\n\n"
+				      "\tSUPPRESS_HANDLE_INHERITANCE_WARNING=1"
+				      "\n");
+		}
+		restrict_handle_inheritance = 0;
+		flags &= ~EXTENDED_STARTUPINFO_PRESENT;
+		ret = CreateProcessW(*wcmd ? wcmd : NULL, wargs, NULL, NULL,
+				     TRUE, flags, wenvblk, dir ? wdir : NULL,
+				     &si.StartupInfo, &pi);
+		if (ret && buf.len) {
+			errno = err_win_to_posix(GetLastError());
+			warning("failed to restrict file handles (%ld)\n\n%s",
+				err, buf.buf);
+		}
+		strbuf_release(&buf);
+	} else if (!ret)
+		errno = err_win_to_posix(GetLastError());
+
+	if (si.lpAttributeList)
+		DeleteProcThreadAttributeList(si.lpAttributeList);
+	if (attr_list)
+		HeapFree(GetProcessHeap(), 0, attr_list);
 
 	free(wenvblk);
 	free(wargs);
 
-	if (!ret) {
-		errno = ENOENT;
+	if (!ret)
 		return -1;
-	}
+
 	CloseHandle(pi.hThread);
 
 	/*
@@ -2685,7 +2782,7 @@ int symlink(const char *target, const char *link)
 	int len;
 
 	/* fail if symlinks are disabled or API is not supported (WinXP) */
-	if (!has_symlinks || !INIT_PROC_ADDR(CreateSymbolicLinkW)) {
+	if (!has_symlinks) {
 		errno = ENOSYS;
 		return -1;
 	}

compat/poll/poll.h

@@ -21,6 +21,21 @@
 #ifndef _GL_POLL_H
 #define _GL_POLL_H
 
+#if defined(_WIN32_WINNT) && _WIN32_WINNT >= 0x600
+/* Vista has its own, socket-only poll() */
+#undef POLLIN
+#undef POLLPRI
+#undef POLLOUT
+#undef POLLERR
+#undef POLLHUP
+#undef POLLNVAL
+#undef POLLRDNORM
+#undef POLLRDBAND
+#undef POLLWRNORM
+#undef POLLWRBAND
+#define pollfd compat_pollfd
+#endif
+
 /* fake a poll(2) environment */
 #define POLLIN      0x0001      /* any readable data available   */
 #define POLLPRI     0x0002      /* OOB/Urgent readable data      */

compat/winansi.c

@@ -660,10 +660,20 @@ void winansi_init(void)
  */
 HANDLE winansi_get_osfhandle(int fd)
 {
+	HANDLE ret;
+
 	if (fd == 1 && (fd_is_interactive[1] & FD_SWAPPED))
 		return hconsole1;
 	if (fd == 2 && (fd_is_interactive[2] & FD_SWAPPED))
 		return hconsole2;
 
-	return (HANDLE)_get_osfhandle(fd);
+	ret = (HANDLE)_get_osfhandle(fd);
+
+	/*
+	 * There are obviously circumstances under which _get_osfhandle()
+	 * returns (HANDLE)-2. This is not documented anywhere, but that is so
+	 * clearly an invalid handle value that we can just work around this
+	 * and return the correct value for invalid handles.
+	 */
+	return ret == (HANDLE)-2 ? INVALID_HANDLE_VALUE : ret;
 }

config.mak.uname

@@ -407,8 +407,6 @@ ifeq ($(uname_S),Windows)
 	NO_GETTEXT = YesPlease
 	NO_PYTHON = YesPlease
 	ETAGS_TARGET = ETAGS
-	NO_INET_PTON = YesPlease
-	NO_INET_NTOP = YesPlease
 	NO_POSIX_GOODIES = UnfortunatelyYes
 	NATIVE_CRLF = YesPlease
 	DEFAULT_HELP_FORMAT = html
@@ -577,8 +575,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	NO_REGEX = YesPlease
 	NO_PYTHON = YesPlease
 	ETAGS_TARGET = ETAGS
-	NO_INET_PTON = YesPlease
-	NO_INET_NTOP = YesPlease
 	NO_POSIX_GOODIES = UnfortunatelyYes
 	DEFAULT_HELP_FORMAT = html
 	COMPAT_CFLAGS += -DNOGDI -Icompat -Icompat/win32

git-compat-util.h

@@ -155,8 +155,8 @@
 #define _SGI_SOURCE 1
 
 #if defined(WIN32) && !defined(__CYGWIN__) /* Both MinGW and MSVC */
-# if defined (_MSC_VER) && !defined(_WIN32_WINNT)
-#  define _WIN32_WINNT 0x0502
+# if !defined(_WIN32_WINNT)
+#  define _WIN32_WINNT 0x0600
 # endif
 #define WIN32_LEAN_AND_MEAN  /* stops windows.h including winsock.h */
 #include <winsock2.h>

t/helper/test-run-command.c

@@ -190,13 +190,58 @@ static int testsuite(int argc, const char **argv)
 	return !!ret;
 }
 
+static int inherit_handle(const char *argv0)
+{
+	struct child_process cp = CHILD_PROCESS_INIT;
+	char path[PATH_MAX];
+	int tmp;
+
+	/* First, open an inheritable handle */
+	sprintf(path, "out-XXXXXX");
+	tmp = xmkstemp(path);
+
+	argv_array_pushl(&cp.args, argv0, "inherited-handle-child", NULL);
+	cp.in = -1;
+	cp.no_stdout = cp.no_stderr = 1;
+	if (start_command(&cp) < 0)
+		die("Could not start child process");
+
+	/* Then close it, and try to delete it. */
+	close(tmp);
+	if (unlink(path))
+		die("Could not delete '%s'", path);
+
+	if (close(cp.in) < 0 || finish_command(&cp) < 0)
+		die("Child did not finish");
+
+	return 0;
+}
+
+static int inherit_handle_child(void)
+{
+	struct strbuf buf = STRBUF_INIT;
+
+	if (strbuf_read(&buf, 0, 0) < 0)
+		die("Could not read stdin");
+	printf("Received %s\n", buf.buf);
+	strbuf_release(&buf);
+
+	return 0;
+}
+
 int cmd__run_command(int argc, const char **argv)
 {
 	struct child_process proc = CHILD_PROCESS_INIT;
 	int jobs;
 
 	if (argc > 1 && !strcmp(argv[1], "testsuite"))
 		exit(testsuite(argc - 1, argv + 1));
+
+	if (!strcmp(argv[1], "inherited-handle"))
+		exit(inherit_handle(argv[0]));
+	if (!strcmp(argv[1], "inherited-handle-child"))
+		exit(inherit_handle_child());
+
 	if (argc < 3)
 		return 1;
 	while (!strcmp(argv[1], "env")) {

t/t0061-run-command.sh

@@ -13,6 +13,10 @@ cat >hello-script <<-EOF
 EOF
 >empty
 
+test_expect_success MINGW 'subprocess inherits only std handles' '
+	test-run-command inherited-handle
+'
+
 test_expect_success 'start_command reports ENOENT' '
 	test-tool run-command start-command-ENOENT ./does-not-exist
 '