lstat should resolve the final path component if it ends in a slash.

PiperOrigin-RevId: 239896221
Change-Id: I0949981fe50c57131c5631cdeb10b225648575c0

pkg/sentry/syscalls/linux/sys_stat.go

@@ -78,7 +78,11 @@ func Lstat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 		return 0, nil, err
 	}
 
-	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, false /* resolve */, func(root *fs.Dirent, d *fs.Dirent) error {
+	// If the path ends in a slash (i.e. dirPath is true), then we *do*
+	// want to resolve the final component.
+	resolve := dirPath
+
+	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, resolve, func(root *fs.Dirent, d *fs.Dirent) error {
 		return stat(t, d, dirPath, statAddr)
 	})
 }

test/syscalls/linux/stat.cc

@@ -374,6 +374,31 @@ TEST_F(StatTest, ChildOfNonDir) {
   EXPECT_THAT(lstat(filename.c_str(), &st), SyscallFailsWithErrno(ENOTDIR));
 }
 
+// Test lstating a symlink directory.
+TEST_F(StatTest, LstatSymlinkDir) {
+  // Create a directory and symlink to it.
+  const auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  const std::string symlink_to_dir = NewTempAbsPath();
+  EXPECT_THAT(symlink(dir.path().c_str(), symlink_to_dir.c_str()),
+              SyscallSucceeds());
+  auto cleanup = Cleanup([&symlink_to_dir]() {
+    EXPECT_THAT(unlink(symlink_to_dir.c_str()), SyscallSucceeds());
+  });
+
+  // Lstat on the symlink should return symlink data.
+  struct stat st = {};
+  ASSERT_THAT(lstat(symlink_to_dir.c_str(), &st), SyscallSucceeds());
+  EXPECT_FALSE(S_ISDIR(st.st_mode));
+  EXPECT_TRUE(S_ISLNK(st.st_mode));
+
+  // Lstat on the symlink with a trailing slash should return the directory
+  // data.
+  ASSERT_THAT(lstat(absl::StrCat(symlink_to_dir, "/").c_str(), &st),
+              SyscallSucceeds());
+  EXPECT_TRUE(S_ISDIR(st.st_mode));
+  EXPECT_FALSE(S_ISLNK(st.st_mode));
+}
+
 // Verify that we get an ELOOP from too many symbolic links even when there
 // are directories in the middle.
 TEST_F(StatTest, LstatELOOPPath) {