[vfs] overlayfs: Fix socket tests.

- BindSocketThenOpen test was expecting the incorrect error when opening
  a socket. Fixed that.
- VirtualFilesystem.BindEndpointAt should not require pop.Path.Begin.Ok()
  because the filesystem implementations do not need to walk to the parent
  dentry. This check also exists for MknodAt, MkdirAt, RmdirAt, SymlinkAt and
  UnlinkAt but those filesystem implementations also need to walk to the parent
  denty. So that check is valid. Added some syscall tests to test this.

PiperOrigin-RevId: 330625220

1 files changed, 10 insertions, 0 deletions

diff --git a/test/syscalls/linux/symlink.cc b/test/syscalls/linux/symlink.cc
index aa1f32c85..a5d7efe94 100644
--- a/test/syscalls/linux/symlink.cc
+++ b/test/syscalls/linux/symlink.cc
@@ -326,6 +326,16 @@ TEST(SymlinkTest, FollowUpdatesATime) {
   EXPECT_LT(st_before_follow.st_atime, st_after_follow.st_atime);
 }
 
+TEST(SymlinkTest, SymlinkAtEmptyPath) {
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+
+  auto fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_RDONLY | O_DIRECTORY, 0666));
+  EXPECT_THAT(symlinkat(file.path().c_str(), fd.get(), ""),
+              SyscallFailsWithErrno(ENOENT));
+}
+
 class ParamSymlinkTest : public ::testing::TestWithParam<std::string> {};
 
 // Test that creating an existing symlink with creat will create the target.