Add syscall test for rename when an writable FD exists and file perms changed.

The gofer server should not attempt to re-open the writable FD on server on
rename. runsc/fsgofer works as expected.

PiperOrigin-RevId: 429197853

test/syscalls/linux/BUILD

@@ -2148,6 +2148,7 @@ cc_binary(
         "//test/util:fs_util",
         "@com_google_absl//absl/strings",
         gtest,
+        "//test/util:save_util",
         "//test/util:temp_path",
         "//test/util:test_main",
         "//test/util:test_util",

test/syscalls/linux/rename.cc

@@ -23,6 +23,7 @@
 #include "test/util/cleanup.h"
 #include "test/util/file_descriptor.h"
 #include "test/util/fs_util.h"
+#include "test/util/save_util.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
 
@@ -87,6 +88,19 @@ TEST(RenameTest, FileToSameDirectory) {
   EXPECT_THAT(Exists(newpath), IsPosixErrorOkAndHolds(true));
 }
 
+TEST(RenameTest, RenameAfterWritableFDAndChmod) {
+  // Restore will require re-opening the writable FD which will fail.
+  const DisableSave ds;
+  const std::string data = "hello world\n";
+  auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  auto wfd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_WRONLY));
+  ASSERT_THAT(chmod(f.path().c_str(), 0444), SyscallSucceeds());
+  std::string const newpath = NewTempAbsPath();
+  ASSERT_THAT(rename(f.path().c_str(), newpath.c_str()), SyscallSucceeds());
+  EXPECT_THAT(WriteFd(wfd.get(), data.c_str(), data.size()),
+              SyscallSucceedsWithValue(data.size()));
+}
+
 TEST(RenameTest, DirectoryToSameDirectory) {
   auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
   std::string const newpath = NewTempAbsPath();