inotify notifies watchers when control events bit are set

The code that matches the event being published with events watchers
was wronly matching all watchers in case any of the control event bits
were set.

Issue #121

PiperOrigin-RevId: 226521230
Change-Id: Ie2c42bc4366faaf59fbf80a74e9297499bd93f9e

pkg/sentry/fs/inotify_watch.go

@@ -76,15 +76,17 @@ func isRenameEvent(eventMask uint32) bool {
 
 // Notify queues a new event on this watch.
 func (w *Watch) Notify(name string, events uint32, cookie uint32) {
-	unmaskableBits := ^uint32(0) &^ linux.IN_ALL_EVENTS
-	effectiveMask := unmaskableBits | atomic.LoadUint32(&w.mask)
-	matchedEvents := effectiveMask & events
-
-	if matchedEvents == 0 {
+	mask := atomic.LoadUint32(&w.mask)
+	if mask&events == 0 {
 		// We weren't watching for this event.
 		return
 	}
 
+	// Event mask should include bits matched from the watch plus all control
+	// event bits.
+	unmaskableBits := ^uint32(0) &^ linux.IN_ALL_EVENTS
+	effectiveMask := unmaskableBits | mask
+	matchedEvents := effectiveMask & events
 	w.owner.queueEvent(newEvent(w.wd, name, matchedEvents, cookie))
 }
 

pkg/sentry/strace/linux64.go

@@ -271,7 +271,7 @@ var linuxAMD64 = SyscallMap{
 	251: makeSyscallInfo("ioprio_set", Hex, Hex, Hex),
 	252: makeSyscallInfo("ioprio_get", Hex, Hex),
 	253: makeSyscallInfo("inotify_init"),
-	254: makeSyscallInfo("inotify_add_watch", Hex, Hex, Hex),
+	254: makeSyscallInfo("inotify_add_watch", Hex, Path, Hex),
 	255: makeSyscallInfo("inotify_rm_watch", Hex, Hex),
 	256: makeSyscallInfo("migrate_pages", Hex, Hex, Hex, Hex),
 	257: makeSyscallInfo("openat", Hex, Path, OpenFlags, Mode),

test/syscalls/linux/inotify.cc

@@ -1484,6 +1484,34 @@ TEST(Inotify, MaskAddMergesWithExistingEventMask) {
   ASSERT_THAT(events, Are({Event(IN_CLOSE_WRITE, wd)}));
 }
 
+// Test that control events bits are not considered when checking event mask.
+TEST(Inotify, ControlEvents) {
+  const TempPath dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(InotifyInit1(IN_NONBLOCK));
+
+  const int wd = ASSERT_NO_ERRNO_AND_VALUE(
+      InotifyAddWatch(fd.get(), dir.path(), IN_ACCESS));
+
+  // Check that events in the mask are dispatched and that control bits are
+  // part of the event mask.
+  std::vector<std::string> files =
+      ASSERT_NO_ERRNO_AND_VALUE(ListDir(dir.path(), false));
+  ASSERT_EQ(files.size(), 2);
+
+  const std::vector<Event> events1 =
+      ASSERT_NO_ERRNO_AND_VALUE(DrainEvents(fd.get()));
+  ASSERT_THAT(events1, Are({Event(IN_ACCESS | IN_ISDIR, wd)}));
+
+  // Check that events not in the mask are discarded.
+  const FileDescriptor dir_fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_RDONLY | O_DIRECTORY));
+
+  const std::vector<Event> events2 =
+      ASSERT_NO_ERRNO_AND_VALUE(DrainEvents(fd.get()));
+  ASSERT_THAT(events2, Are({}));
+}
+
 }  // namespace
 }  // namespace testing
 }  // namespace gvisor