Fix //test/syscalls:exec_test_native

Later kernels add empty arguments to argv, throwing off return values for the
exec_basic_workload.cc binary. This is result of a bug introduced by
ccbb18b67323b "exec/binfmt_script: Don't modify bprm->buf and then return -
ENOEXEC". Before this change, an empty interpreter string was reported if the
first non-space/non-tab character after "#!" was '\0' (end of file, previously-
overwritten trailing space or tab, or previously-overwritten first newline).
After this change, an empty interpreter string is reported if all characters
after "#!" are spaces or tabs, or the first non-space non-tab character is at
i_end, which is the position of the first newline after "#!". However, if
there is no newline after "#!" (as in ExecTest.InterpreterScriptNoPath),
then i_end = buf_end (= bprm->buf + sizeof(bprm->buf) - 1, the last possible
byte in the buffer) and neither condition holds.

Change white space for script inputs to take into account the above bug.

Co-authored-by: Andrei Vagin <avagin@gmail.com>
PiperOrigin-RevId: 378997171

2 files changed, 6 insertions, 9 deletions

diff --git a/pkg/sentry/loader/interpreter.go b/pkg/sentry/loader/interpreter.go
index 3886b4d33..3e302d92c 100644
--- a/pkg/sentry/loader/interpreter.go
+++ b/pkg/sentry/loader/interpreter.go
@@ -59,7 +59,7 @@ func parseInterpreterScript(ctx context.Context, filename string, f fsbridge.Fil
 	// Linux silently truncates the remainder of the line if it exceeds
 	// interpMaxLineLength.
 	i := bytes.IndexByte(line, '\n')
-	if i > 0 {
+	if i >= 0 {
 		line = line[:i]
 	}
 
diff --git a/test/syscalls/linux/exec.cc b/test/syscalls/linux/exec.cc
index e0f3779a2..4df429ed8 100644
--- a/test/syscalls/linux/exec.cc
+++ b/test/syscalls/linux/exec.cc
@@ -278,15 +278,12 @@ TEST(ExecTest, InterpreterScriptArgNUL) {
 
 // Trailing whitespace following interpreter path is ignored.
 TEST(ExecTest, InterpreterScriptTrailingWhitespace) {
-  // FIXME(b/190850365): This test case fails on Linux.
-  SKIP_IF(!IsRunningOnGvisor());
-
   // Symlink through /tmp to ensure the path is short enough.
   TempPath link = ASSERT_NO_ERRNO_AND_VALUE(
       TempPath::CreateSymlinkTo("/tmp", RunfilePath(kBasicWorkload)));
 
   TempPath script = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileWith(
-      GetAbsoluteTestTmpdir(), absl::StrCat("#!", link.path(), "  "), 0755));
+      GetAbsoluteTestTmpdir(), absl::StrCat("#!", link.path(), "  \n"), 0755));
 
   CheckExec(script.path(), {script.path()}, {}, ArgEnvExitStatus(1, 0),
             absl::StrCat(link.path(), "\n", script.path(), "\n"));
@@ -306,11 +303,11 @@ TEST(ExecTest, InterpreterScriptArgWhitespace) {
 }
 
 TEST(ExecTest, InterpreterScriptNoPath) {
-  // FIXME(b/190850365): This test case fails on Linux.
-  SKIP_IF(!IsRunningOnGvisor());
-
   TempPath script = ASSERT_NO_ERRNO_AND_VALUE(
-      TempPath::CreateFileWith(GetAbsoluteTestTmpdir(), "#!", 0755));
+      TempPath::CreateFileWith(GetAbsoluteTestTmpdir(), "#!\n\n", 0755));
+
+  std::cerr << "path: " << script.path() << std::endl;
+  std::cerr << system(absl::StrCat("cat ", script.path()).c_str()) << std::endl;
 
   int execve_errno;
   ASSERT_NO_ERRNO_AND_VALUE(