Add FIONREAD to host file description

Closes #8544

PiperOrigin-RevId: 535456427

images/basic/integrationtest/host_fd.c

@@ -14,12 +14,17 @@
 
 #include <err.h>
 #include <errno.h>
+#include <getopt.h>
 #include <stddef.h>
+#include <stdio.h>
 #include <sys/epoll.h>
 #include <sys/ioctl.h>
 #include <sys/select.h>
 #include <unistd.h>
 
+// Flag to indicate that TTY is being used in the container.
+static int tty = 0;
+
 // Tests that FIONREAD is supported with host FD.
 void testFionread() {
   int size = 0;
@@ -34,6 +39,10 @@ void testFionread() {
 // Docker maps stdin to /dev/null which doesn't support epoll. Check that error
 // is correctly propagated.
 void testEpoll() {
+  if (tty) {
+    // stdin is not /dev/null when TTY is used for the container.
+    return;
+  }
   int fd = epoll_create(1);
   if (fd < 0) {
     err(1, "epoll_create");
@@ -67,6 +76,18 @@ void testSelect() {
 }
 
 int main(int argc, char** argv) {
+  int opt;
+  while ((opt = getopt(argc, argv, "t")) != -1) {
+    switch (opt) {
+      case 't':
+        tty = 1;
+        break;
+      default:
+        fprintf(stderr, "Usage: %s [-t]\n", argv[0]);
+        return 1;
+    }
+  }
+
   testFionread();
   testEpoll();
   testSelect();

pkg/sentry/fsimpl/host/tty.go

@@ -18,6 +18,7 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/errors/linuxerr"
+	"gvisor.dev/gvisor/pkg/hostarch"
 	"gvisor.dev/gvisor/pkg/marshal/primitive"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
@@ -154,6 +155,17 @@ func (t *TTYFileDescription) Ioctl(ctx context.Context, io usermem.IO, sysno uin
 	fd := t.inode.hostFD
 	ioctl := args[1].Uint64()
 	switch ioctl {
+	case linux.FIONREAD:
+		v, err := ioctlFionread(fd)
+		if err != nil {
+			return 0, err
+		}
+
+		var buf [4]byte
+		hostarch.ByteOrder.PutUint32(buf[:], v)
+		_, err = io.CopyOut(ctx, args[2].Pointer(), buf[:], usermem.IOOpts{})
+		return 0, err
+
 	case linux.TCGETS:
 		termios, err := ioctlGetTermios(fd)
 		if err != nil {

test/e2e/integration_test.go

@@ -533,7 +533,32 @@ func TestStickyDir(t *testing.T) {
 }
 
 func TestHostFD(t *testing.T) {
-	runIntegrationTest(t, nil, "./host_fd")
+	t.Run("regular", func(t *testing.T) {
+		runIntegrationTest(t, nil, "./host_fd")
+	})
+	t.Run("tty", func(t *testing.T) {
+		ctx := context.Background()
+		d := dockerutil.MakeContainer(ctx, t)
+		defer d.CleanUp(ctx)
+
+		// Start the container with an attached PTY.
+		p, err := d.SpawnProcess(ctx, dockerutil.RunOpts{
+			Image:   "basic/integrationtest",
+			WorkDir: "/root",
+		}, "./host_fd", "-t")
+		if err != nil {
+			t.Fatalf("docker run failed: %v", err)
+		}
+
+		if err := d.Wait(ctx); err != nil {
+			t.Fatalf("Wait failed: %v", err)
+		}
+		if out, err := p.Logs(); err != nil {
+			t.Fatal(err)
+		} else if len(out) > 0 {
+			t.Errorf("test failed:\n%s", out)
+		}
+	})
 }
 
 func runIntegrationTest(t *testing.T, capAdd []string, args ...string) {