From aade3a56b5a5b7ce2adf1c7035a6d10bc538ec9d Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@google.com>
Date: Thu, 12 Jan 2023 12:30:25 -0800
Subject: [PATCH] Don't register async handlers for signalfd descriptors

This is a missing part of cl/483861398.

PiperOrigin-RevId: 501636729
---
 pkg/sentry/vfs/file_description.go |  4 ++--
 test/syscalls/linux/fcntl.cc       | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/pkg/sentry/vfs/file_description.go b/pkg/sentry/vfs/file_description.go
index d54f97f00..d76d09545 100644
--- a/pkg/sentry/vfs/file_description.go
+++ b/pkg/sentry/vfs/file_description.go
@@ -276,6 +276,7 @@ func (fd *FileDescription) SetStatusFlags(ctx context.Context, creds *auth.Crede
 	// TODO(gvisor.dev/issue/1035): FileDescriptionImpl.SetOAsync()?
 	const settableFlags = linux.O_APPEND | linux.O_ASYNC | linux.O_DIRECT | linux.O_NOATIME | linux.O_NONBLOCK
 	fd.flagsMu.Lock()
+	defer fd.flagsMu.Unlock()
 	if fd.asyncHandler != nil {
 		// Use fd.statusFlags instead of oldFlags, which may have become outdated,
 		// to avoid double registering/unregistering.
@@ -288,7 +289,6 @@ func (fd *FileDescription) SetStatusFlags(ctx context.Context, creds *auth.Crede
 		}
 	}
 	fd.statusFlags.Store((oldFlags &^ settableFlags) | (flags & settableFlags))
-	fd.flagsMu.Unlock()
 	return nil
 }
 
@@ -944,7 +944,7 @@ func (fd *FileDescription) SetAsyncHandler(newHandler func() FileAsync) (FileAsy
 	if fd.asyncHandler == nil {
 		fd.asyncHandler = newHandler()
 		if fd.statusFlags.RacyLoad()&linux.O_ASYNC != 0 {
-			if err := fd.asyncHandler.Register(fd); err != nil {
+			if err := fd.impl.RegisterFileAsyncHandler(fd); err != nil {
 				return nil, err
 			}
 		}
diff --git a/test/syscalls/linux/fcntl.cc b/test/syscalls/linux/fcntl.cc
index 94696409e..db5edfed3 100644
--- a/test/syscalls/linux/fcntl.cc
+++ b/test/syscalls/linux/fcntl.cc
@@ -1510,6 +1510,25 @@ TEST_F(FcntlSignalTest, SignalFD) {
   syscall(SYS_tkill, tid, SIGIO);
 }
 
+TEST_F(FcntlSignalTest, SignalFDSetSigAfterASYNC) {
+  // Create the signalfd.
+  sigset_t mask;
+  sigemptyset(&mask);
+  sigaddset(&mask, SIGIO);
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(NewSignalFD(&mask, 0));
+
+  const auto signal_cleanup =
+      ASSERT_NO_ERRNO_AND_VALUE(RegisterSignalHandler(SIGIO));
+  ASSERT_THAT(fcntl(fd.get(), F_SETOWN, getpid()), SyscallSucceeds());
+  int old_flags;
+  ASSERT_THAT(old_flags = fcntl(fd.get(), F_GETFL), SyscallSucceeds());
+  ASSERT_THAT(fcntl(fd.get(), F_SETFL, old_flags | O_ASYNC), SyscallSucceeds());
+  ASSERT_THAT(fcntl(fd.get(), F_SETSIG, 0), SyscallSucceeds());
+
+  int tid = syscall(SYS_gettid);
+  syscall(SYS_tkill, tid, SIGIO);
+}
+
 TEST_F(FcntlSignalTest, SetSigCustom) {
   const auto signal_cleanup =
       ASSERT_NO_ERRNO_AND_VALUE(RegisterSignalHandler(SIGUSR1));