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

3 files changed, 36 insertions, 6 deletions

diff --git a/pkg/sentry/fs/inotify_watch.go b/pkg/sentry/fs/inotify_watch.go
index b83544c9f..d33e7e498 100644
--- a/pkg/sentry/fs/inotify_watch.go
+++ b/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))
 }
 
diff --git a/pkg/sentry/strace/linux64.go b/pkg/sentry/strace/linux64.go
index e8fb711a5..de2da9369 100644
--- a/pkg/sentry/strace/linux64.go
+++ b/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),
diff --git a/test/syscalls/linux/inotify.cc b/test/syscalls/linux/inotify.cc
index 62fc55c72..0e361496c 100644
--- a/test/syscalls/linux/inotify.cc
+++ b/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