Assign controlling terminal when tty is opened and support NOCTTY

PiperOrigin-RevId: 357015186

4 files changed, 68 insertions, 2 deletions

diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 42fc363a2..31dc2525c 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -1441,6 +1441,7 @@ cc_binary(
         "@com_google_absl//absl/synchronization",
         "@com_google_absl//absl/time",
         gtest,
+        "//test/util:cleanup",
         "//test/util:posix_error",
         "//test/util:pty_util",
         "//test/util:test_main",
diff --git a/test/syscalls/linux/pty.cc b/test/syscalls/linux/pty.cc
index 85ff258df..e6b12f81c 100644
--- a/test/syscalls/linux/pty.cc
+++ b/test/syscalls/linux/pty.cc
@@ -36,6 +36,7 @@
 #include "absl/time/clock.h"
 #include "absl/time/time.h"
 #include "test/util/capability_util.h"
+#include "test/util/cleanup.h"
 #include "test/util/file_descriptor.h"
 #include "test/util/posix_error.h"
 #include "test/util/pty_util.h"
@@ -459,6 +460,59 @@ TEST(BasicPtyTest, OpenMasterReplica) {
   FileDescriptor replica = ASSERT_NO_ERRNO_AND_VALUE(OpenReplica(master));
 }
 
+TEST(BasicPtyTest, OpenSetsControllingTTY) {
+  SKIP_IF(IsRunningWithVFS1());
+  // setsid either puts us in a new session or fails because we're already the
+  // session leader. Either way, this ensures we're the session leader.
+  setsid();
+
+  // Make sure we're ignoring SIGHUP, which will be sent to this process once we
+  // disconnect they TTY.
+  struct sigaction sa = {};
+  sa.sa_handler = SIG_IGN;
+  sa.sa_flags = 0;
+  sigemptyset(&sa.sa_mask);
+  struct sigaction old_sa;
+  ASSERT_THAT(sigaction(SIGHUP, &sa, &old_sa), SyscallSucceeds());
+  auto cleanup = Cleanup([old_sa] {
+    EXPECT_THAT(sigaction(SIGHUP, &old_sa, NULL), SyscallSucceeds());
+  });
+
+  FileDescriptor master = ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/ptmx", O_RDWR));
+  FileDescriptor replica =
+      ASSERT_NO_ERRNO_AND_VALUE(OpenReplica(master, O_NONBLOCK | O_RDWR));
+
+  // Opening replica should make it our controlling TTY, and therefore we are
+  // able to give it up.
+  ASSERT_THAT(ioctl(replica.get(), TIOCNOTTY), SyscallSucceeds());
+}
+
+TEST(BasicPtyTest, OpenMasterDoesNotSetsControllingTTY) {
+  SKIP_IF(IsRunningWithVFS1());
+  // setsid either puts us in a new session or fails because we're already the
+  // session leader. Either way, this ensures we're the session leader.
+  setsid();
+  FileDescriptor master = ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/ptmx", O_RDWR));
+
+  // Opening master does not set the controlling TTY, and therefore we are
+  // unable to give it up.
+  ASSERT_THAT(ioctl(master.get(), TIOCNOTTY), SyscallFailsWithErrno(ENOTTY));
+}
+
+TEST(BasicPtyTest, OpenNOCTTY) {
+  SKIP_IF(IsRunningWithVFS1());
+  // setsid either puts us in a new session or fails because we're already the
+  // session leader. Either way, this ensures we're the session leader.
+  setsid();
+  FileDescriptor master = ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/ptmx", O_RDWR));
+  FileDescriptor replica = ASSERT_NO_ERRNO_AND_VALUE(
+      OpenReplica(master, O_NOCTTY | O_NONBLOCK | O_RDWR));
+
+  // Opening replica with O_NOCTTY won't make it our controlling TTY, and
+  // therefore we are unable to give it up.
+  ASSERT_THAT(ioctl(replica.get(), TIOCNOTTY), SyscallFailsWithErrno(ENOTTY));
+}
+
 // The replica entry in /dev/pts/ disappears when the master is closed, even if
 // the replica is still open.
 TEST(BasicPtyTest, ReplicaEntryGoneAfterMasterClose) {
diff --git a/test/util/pty_util.cc b/test/util/pty_util.cc
index 2cf0bea74..351f4730c 100644
--- a/test/util/pty_util.cc
+++ b/test/util/pty_util.cc
@@ -24,11 +24,16 @@ namespace gvisor {
 namespace testing {
 
 PosixErrorOr<FileDescriptor> OpenReplica(const FileDescriptor& master) {
+  return OpenReplica(master, O_NONBLOCK | O_RDWR | O_NOCTTY);
+}
+
+PosixErrorOr<FileDescriptor> OpenReplica(const FileDescriptor& master,
+                                         int flags) {
   PosixErrorOr<int> n = ReplicaID(master);
   if (!n.ok()) {
     return PosixErrorOr<FileDescriptor>(n.error());
   }
-  return Open(absl::StrCat("/dev/pts/", n.ValueOrDie()), O_RDWR | O_NONBLOCK);
+  return Open(absl::StrCat("/dev/pts/", n.ValueOrDie()), flags);
 }
 
 PosixErrorOr<int> ReplicaID(const FileDescriptor& master) {
diff --git a/test/util/pty_util.h b/test/util/pty_util.h
index ed7658868..0cca2182c 100644
--- a/test/util/pty_util.h
+++ b/test/util/pty_util.h
@@ -21,9 +21,15 @@
 namespace gvisor {
 namespace testing {
 
-// Opens the replica end of the passed master as R/W and nonblocking.
+// Opens the replica end of the passed master as R/W and nonblocking. It does
+// not set the replica as the controlling TTY.
 PosixErrorOr<FileDescriptor> OpenReplica(const FileDescriptor& master);
 
+// Identical to the above OpenReplica, but flags are all specified by the
+// caller.
+PosixErrorOr<FileDescriptor> OpenReplica(const FileDescriptor& master,
+                                         int flags);
+
 // Get the number of the replica end of the master.
 PosixErrorOr<int> ReplicaID(const FileDescriptor& master);