Add O_PATH support in vfs2

PiperOrigin-RevId: 354367665

36 files changed, 837 insertions, 18 deletions

diff --git a/pkg/sentry/syscalls/linux/vfs2/fd.go b/pkg/sentry/syscalls/linux/vfs2/fd.go
index e39f074f2..1a31898e8 100644
--- a/pkg/sentry/syscalls/linux/vfs2/fd.go
+++ b/pkg/sentry/syscalls/linux/vfs2/fd.go
@@ -123,6 +123,15 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	}
 	defer file.DecRef(t)
 
+	if file.StatusFlags()&linux.O_PATH != 0 {
+		switch cmd {
+		case linux.F_DUPFD, linux.F_DUPFD_CLOEXEC, linux.F_GETFD, linux.F_SETFD, linux.F_GETFL:
+			// allowed
+		default:
+			return 0, nil, syserror.EBADF
+		}
+	}
+
 	switch cmd {
 	case linux.F_DUPFD, linux.F_DUPFD_CLOEXEC:
 		minfd := args[2].Int()
@@ -395,6 +404,10 @@ func Fadvise64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sys
 	}
 	defer file.DecRef(t)
 
+	if file.StatusFlags()&linux.O_PATH != 0 {
+		return 0, nil, syserror.EBADF
+	}
+
 	// If the FD refers to a pipe or FIFO, return error.
 	if _, isPipe := file.Impl().(*pipe.VFSPipeFD); isPipe {
 		return 0, nil, syserror.ESPIPE
diff --git a/pkg/sentry/syscalls/linux/vfs2/ioctl.go b/pkg/sentry/syscalls/linux/vfs2/ioctl.go
index 20c264fef..c7c3fed57 100644
--- a/pkg/sentry/syscalls/linux/vfs2/ioctl.go
+++ b/pkg/sentry/syscalls/linux/vfs2/ioctl.go
@@ -32,6 +32,10 @@ func Ioctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 	}
 	defer file.DecRef(t)
 
+	if file.StatusFlags()&linux.O_PATH != 0 {
+		return 0, nil, syserror.EBADF
+	}
+
 	// Handle ioctls that apply to all FDs.
 	switch args[1].Int() {
 	case linux.FIONCLEX:
diff --git a/pkg/sentry/syscalls/linux/vfs2/sync.go b/pkg/sentry/syscalls/linux/vfs2/sync.go
index 6e9b599e2..1f8a5878c 100644
--- a/pkg/sentry/syscalls/linux/vfs2/sync.go
+++ b/pkg/sentry/syscalls/linux/vfs2/sync.go
@@ -36,6 +36,10 @@ func Syncfs(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscal
 	}
 	defer file.DecRef(t)
 
+	if file.StatusFlags()&linux.O_PATH != 0 {
+		return 0, nil, syserror.EBADF
+	}
+
 	return 0, nil, file.SyncFS(t)
 }
 
diff --git a/pkg/sentry/vfs/BUILD b/pkg/sentry/vfs/BUILD
index a3868bf16..df4990854 100644
--- a/pkg/sentry/vfs/BUILD
+++ b/pkg/sentry/vfs/BUILD
@@ -83,6 +83,7 @@ go_library(
         "mount.go",
         "mount_namespace_refs.go",
         "mount_unsafe.go",
+        "opath.go",
         "options.go",
         "pathname.go",
         "permissions.go",
diff --git a/pkg/sentry/vfs/opath.go b/pkg/sentry/vfs/opath.go
new file mode 100644
index 000000000..39fbac987
--- /dev/null
+++ b/pkg/sentry/vfs/opath.go
@@ -0,0 +1,139 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// opathFD implements vfs.FileDescriptionImpl for a file description opened with O_PATH.
+//
+// +stateify savable
+type opathFD struct {
+	vfsfd FileDescription
+	FileDescriptionDefaultImpl
+	NoLockFD
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *opathFD) Release(context.Context) {
+	// noop
+}
+
+// Allocate implements vfs.FileDescriptionImpl.Allocate.
+func (fd *opathFD) Allocate(ctx context.Context, mode, offset, length uint64) error {
+	return syserror.EBADF
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *opathFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts ReadOptions) (int64, error) {
+	return 0, syserror.EBADF
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *opathFD) Read(ctx context.Context, dst usermem.IOSequence, opts ReadOptions) (int64, error) {
+	return 0, syserror.EBADF
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *opathFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts WriteOptions) (int64, error) {
+	return 0, syserror.EBADF
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *opathFD) Write(ctx context.Context, src usermem.IOSequence, opts WriteOptions) (int64, error) {
+	return 0, syserror.EBADF
+}
+
+// Ioctl implements vfs.FileDescriptionImpl.Ioctl.
+func (fd *opathFD) Ioctl(ctx context.Context, uio usermem.IO, args arch.SyscallArguments) (uintptr, error) {
+	return 0, syserror.EBADF
+}
+
+// IterDirents implements vfs.FileDescriptionImpl.IterDirents.
+func (fd *opathFD) IterDirents(ctx context.Context, cb IterDirentsCallback) error {
+	return syserror.EBADF
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *opathFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	return 0, syserror.EBADF
+}
+
+// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
+func (fd *opathFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
+	return syserror.EBADF
+}
+
+// ListXattr implements vfs.FileDescriptionImpl.ListXattr.
+func (fd *opathFD) ListXattr(ctx context.Context, size uint64) ([]string, error) {
+	return nil, syserror.EBADF
+}
+
+// GetXattr implements vfs.FileDescriptionImpl.GetXattr.
+func (fd *opathFD) GetXattr(ctx context.Context, opts GetXattrOptions) (string, error) {
+	return "", syserror.EBADF
+}
+
+// SetXattr implements vfs.FileDescriptionImpl.SetXattr.
+func (fd *opathFD) SetXattr(ctx context.Context, opts SetXattrOptions) error {
+	return syserror.EBADF
+}
+
+// RemoveXattr implements vfs.FileDescriptionImpl.RemoveXattr.
+func (fd *opathFD) RemoveXattr(ctx context.Context, name string) error {
+	return syserror.EBADF
+}
+
+// Sync implements vfs.FileDescriptionImpl.Sync.
+func (fd *opathFD) Sync(ctx context.Context) error {
+	return syserror.EBADF
+}
+
+// SetStat implements vfs.FileDescriptionImpl.SetStat.
+func (fd *opathFD) SetStat(ctx context.Context, opts SetStatOptions) error {
+	return syserror.EBADF
+}
+
+// Stat implements vfs.FileDescriptionImpl.Stat.
+func (fd *opathFD) Stat(ctx context.Context, opts StatOptions) (linux.Statx, error) {
+	vfsObj := fd.vfsfd.vd.mount.vfs
+	rp := vfsObj.getResolvingPath(auth.CredentialsFromContext(ctx), &PathOperation{
+		Root:  fd.vfsfd.vd,
+		Start: fd.vfsfd.vd,
+	})
+	stat, err := fd.vfsfd.vd.mount.fs.impl.StatAt(ctx, rp, opts)
+	vfsObj.putResolvingPath(ctx, rp)
+	return stat, err
+}
+
+// StatFS returns metadata for the filesystem containing the file represented
+// by fd.
+func (fd *opathFD) StatFS(ctx context.Context) (linux.Statfs, error) {
+	vfsObj := fd.vfsfd.vd.mount.vfs
+	rp := vfsObj.getResolvingPath(auth.CredentialsFromContext(ctx), &PathOperation{
+		Root:  fd.vfsfd.vd,
+		Start: fd.vfsfd.vd,
+	})
+	statfs, err := fd.vfsfd.vd.mount.fs.impl.StatFSAt(ctx, rp)
+	vfsObj.putResolvingPath(ctx, rp)
+	return statfs, err
+}
diff --git a/pkg/sentry/vfs/options.go b/pkg/sentry/vfs/options.go
index bc79e5ecc..c9907843c 100644
--- a/pkg/sentry/vfs/options.go
+++ b/pkg/sentry/vfs/options.go
@@ -129,7 +129,7 @@ type OpenOptions struct {
 	//
 	// FilesystemImpls are responsible for implementing the following flags:
 	// O_RDONLY, O_WRONLY, O_RDWR, O_APPEND, O_CREAT, O_DIRECT, O_DSYNC,
-	// O_EXCL, O_NOATIME, O_NOCTTY, O_NONBLOCK, O_PATH, O_SYNC, O_TMPFILE, and
+	// O_EXCL, O_NOATIME, O_NOCTTY, O_NONBLOCK, O_SYNC, O_TMPFILE, and
 	// O_TRUNC. VFS is responsible for handling O_DIRECTORY, O_LARGEFILE, and
 	// O_NOFOLLOW. VFS users are responsible for handling O_CLOEXEC, since file
 	// descriptors are mostly outside the scope of VFS.
diff --git a/pkg/sentry/vfs/vfs.go b/pkg/sentry/vfs/vfs.go
index 6fd1bb0b2..0aff2dd92 100644
--- a/pkg/sentry/vfs/vfs.go
+++ b/pkg/sentry/vfs/vfs.go
@@ -425,6 +425,18 @@ func (vfs *VirtualFilesystem) OpenAt(ctx context.Context, creds *auth.Credential
 		rp.mustBeDir = true
 		rp.mustBeDirOrig = true
 	}
+	if opts.Flags&linux.O_PATH != 0 {
+		vd, err := vfs.GetDentryAt(ctx, creds, pop, &GetDentryOptions{})
+		if err != nil {
+			return nil, err
+		}
+		fd := &opathFD{}
+		if err := fd.vfsfd.Init(fd, opts.Flags, vd.Mount(), vd.Dentry(), &FileDescriptionOptions{}); err != nil {
+			return nil, err
+		}
+		vd.DecRef(ctx)
+		return &fd.vfsfd, err
+	}
 	for {
 		fd, err := rp.mount.fs.impl.OpenAt(ctx, rp, *opts)
 		if err == nil {
diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 0da295e2d..2b4b6f348 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -582,6 +582,7 @@ cc_binary(
         "//test/util:eventfd_util",
         "//test/util:file_descriptor",
         gtest,
+        "//test/util:fs_util",
         "//test/util:posix_error",
         "//test/util:temp_path",
         "//test/util:test_main",
diff --git a/test/syscalls/linux/chmod.cc b/test/syscalls/linux/chmod.cc
index a06b5cfd6..8233df0f8 100644
--- a/test/syscalls/linux/chmod.cc
+++ b/test/syscalls/linux/chmod.cc
@@ -98,6 +98,42 @@ TEST(ChmodTest, FchmodatBadF) {
   ASSERT_THAT(fchmodat(-1, "foo", 0444, 0), SyscallFailsWithErrno(EBADF));
 }
 
+TEST(ChmodTest, FchmodFileWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  ASSERT_THAT(fchmod(fd.get(), 0444), SyscallFailsWithErrno(EBADF));
+}
+
+TEST(ChmodTest, FchmodDirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  const auto fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_DIRECTORY | O_PATH));
+
+  ASSERT_THAT(fchmod(fd.get(), 0444), SyscallFailsWithErrno(EBADF));
+}
+
+TEST(ChmodTest, FchmodatWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  // Drop capabilities that allow us to override file permissions.
+  ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false));
+
+  auto temp_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+
+  const auto parent_fd = ASSERT_NO_ERRNO_AND_VALUE(
+      Open(GetAbsoluteTestTmpdir().c_str(), O_PATH | O_DIRECTORY));
+
+  ASSERT_THAT(
+      fchmodat(parent_fd.get(), std::string(Basename(temp_file.path())).c_str(),
+               0444, 0),
+      SyscallSucceeds());
+
+  EXPECT_THAT(open(temp_file.path().c_str(), O_RDWR),
+              SyscallFailsWithErrno(EACCES));
+}
+
 TEST(ChmodTest, FchmodatNotDir) {
   ASSERT_THAT(fchmodat(-1, "", 0444, 0), SyscallFailsWithErrno(ENOENT));
 }
diff --git a/test/syscalls/linux/chown.cc b/test/syscalls/linux/chown.cc
index 5530ad18f..ff0d39343 100644
--- a/test/syscalls/linux/chown.cc
+++ b/test/syscalls/linux/chown.cc
@@ -48,6 +48,36 @@ TEST(ChownTest, FchownatBadF) {
   ASSERT_THAT(fchownat(-1, "fff", 0, 0, 0), SyscallFailsWithErrno(EBADF));
 }
 
+TEST(ChownTest, FchownFileWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  ASSERT_THAT(fchown(fd.get(), geteuid(), getegid()),
+              SyscallFailsWithErrno(EBADF));
+}
+
+TEST(ChownTest, FchownDirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  const auto fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_DIRECTORY | O_PATH));
+
+  ASSERT_THAT(fchown(fd.get(), geteuid(), getegid()),
+              SyscallFailsWithErrno(EBADF));
+}
+
+TEST(ChownTest, FchownatWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileIn(dir.path()));
+  const auto dirfd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_DIRECTORY | O_PATH));
+  ASSERT_THAT(
+      fchownat(dirfd.get(), file.path().c_str(), geteuid(), getegid(), 0),
+      SyscallSucceeds());
+}
+
 TEST(ChownTest, FchownatEmptyPath) {
   const auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
   const auto fd =
@@ -209,6 +239,14 @@ INSTANTIATE_TEST_SUITE_P(
                             owner, group, 0);
           MaybeSave();
           return errorFromReturn("fchownat-dirfd", rc);
+        },
+        [](const std::string& path, uid_t owner, gid_t group) -> PosixError {
+          ASSIGN_OR_RETURN_ERRNO(auto dirfd, Open(std::string(Dirname(path)),
+                                                  O_DIRECTORY | O_PATH));
+          int rc = fchownat(dirfd.get(), std::string(Basename(path)).c_str(),
+                            owner, group, 0);
+          MaybeSave();
+          return errorFromReturn("fchownat-opathdirfd", rc);
         }));
 
 }  // namespace
diff --git a/test/syscalls/linux/dup.cc b/test/syscalls/linux/dup.cc
index 4f773bc75..ba4e13fb9 100644
--- a/test/syscalls/linux/dup.cc
+++ b/test/syscalls/linux/dup.cc
@@ -18,6 +18,7 @@
 #include "gtest/gtest.h"
 #include "test/util/eventfd_util.h"
 #include "test/util/file_descriptor.h"
+#include "test/util/fs_util.h"
 #include "test/util/posix_error.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
@@ -44,14 +45,6 @@ PosixErrorOr<FileDescriptor> Dup3(const FileDescriptor& fd, int target_fd,
   return FileDescriptor(new_fd);
 }
 
-void CheckSameFile(const FileDescriptor& fd1, const FileDescriptor& fd2) {
-  struct stat stat_result1, stat_result2;
-  ASSERT_THAT(fstat(fd1.get(), &stat_result1), SyscallSucceeds());
-  ASSERT_THAT(fstat(fd2.get(), &stat_result2), SyscallSucceeds());
-  EXPECT_EQ(stat_result1.st_dev, stat_result2.st_dev);
-  EXPECT_EQ(stat_result1.st_ino, stat_result2.st_ino);
-}
-
 TEST(DupTest, Dup) {
   auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_RDONLY));
@@ -59,7 +52,7 @@ TEST(DupTest, Dup) {
   // Dup the descriptor and make sure it's the same file.
   FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
   ASSERT_NE(fd.get(), nfd.get());
-  CheckSameFile(fd, nfd);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
 }
 
 TEST(DupTest, DupClearsCloExec) {
@@ -70,10 +63,24 @@ TEST(DupTest, DupClearsCloExec) {
   // Duplicate the descriptor. Ensure that it doesn't have FD_CLOEXEC set.
   FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
   ASSERT_NE(fd.get(), nfd.get());
-  CheckSameFile(fd, nfd);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
   EXPECT_THAT(fcntl(nfd.get(), F_GETFD), SyscallSucceedsWithValue(0));
 }
 
+TEST(DupTest, DupWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_PATH));
+  int flags;
+  ASSERT_THAT(flags = fcntl(fd.get(), F_GETFL), SyscallSucceeds());
+
+  // Dup the descriptor and make sure it's the same file.
+  FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
+  ASSERT_NE(fd.get(), nfd.get());
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFL), SyscallSucceedsWithValue(flags));
+}
+
 TEST(DupTest, Dup2) {
   auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_RDONLY));
@@ -82,13 +89,13 @@ TEST(DupTest, Dup2) {
   FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
 
   ASSERT_NE(fd.get(), nfd.get());
-  CheckSameFile(fd, nfd);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
 
   // Dup over the file above.
   int target_fd = nfd.release();
   FileDescriptor nfd2 = ASSERT_NO_ERRNO_AND_VALUE(Dup2(fd, target_fd));
   EXPECT_EQ(target_fd, nfd2.get());
-  CheckSameFile(fd, nfd2);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd2));
 }
 
 TEST(DupTest, Dup2SameFD) {
@@ -99,6 +106,28 @@ TEST(DupTest, Dup2SameFD) {
   ASSERT_THAT(dup2(fd.get(), fd.get()), SyscallSucceedsWithValue(fd.get()));
 }
 
+TEST(DupTest, Dup2WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_PATH));
+  int flags;
+  ASSERT_THAT(flags = fcntl(fd.get(), F_GETFL), SyscallSucceeds());
+
+  // Regular dup once.
+  FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
+
+  ASSERT_NE(fd.get(), nfd.get());
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFL), SyscallSucceedsWithValue(flags));
+
+  // Dup over the file above.
+  int target_fd = nfd.release();
+  FileDescriptor nfd2 = ASSERT_NO_ERRNO_AND_VALUE(Dup2(fd, target_fd));
+  EXPECT_EQ(target_fd, nfd2.get());
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd2));
+  EXPECT_THAT(fcntl(nfd2.get(), F_GETFL), SyscallSucceedsWithValue(flags));
+}
+
 TEST(DupTest, Dup3) {
   auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_RDONLY));
@@ -106,16 +135,16 @@ TEST(DupTest, Dup3) {
   // Regular dup once.
   FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
   ASSERT_NE(fd.get(), nfd.get());
-  CheckSameFile(fd, nfd);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
 
   // Dup over the file above, check that it has no CLOEXEC.
   nfd = ASSERT_NO_ERRNO_AND_VALUE(Dup3(fd, nfd.release(), 0));
-  CheckSameFile(fd, nfd);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
   EXPECT_THAT(fcntl(nfd.get(), F_GETFD), SyscallSucceedsWithValue(0));
 
   // Dup over the file again, check that it does not CLOEXEC.
   nfd = ASSERT_NO_ERRNO_AND_VALUE(Dup3(fd, nfd.release(), O_CLOEXEC));
-  CheckSameFile(fd, nfd);
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
   EXPECT_THAT(fcntl(nfd.get(), F_GETFD), SyscallSucceedsWithValue(FD_CLOEXEC));
 }
 
@@ -127,6 +156,32 @@ TEST(DupTest, Dup3FailsSameFD) {
   ASSERT_THAT(dup3(fd.get(), fd.get(), 0), SyscallFailsWithErrno(EINVAL));
 }
 
+TEST(DupTest, Dup3WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_PATH));
+  EXPECT_THAT(fcntl(fd.get(), F_GETFD), SyscallSucceedsWithValue(0));
+  int flags;
+  ASSERT_THAT(flags = fcntl(fd.get(), F_GETFL), SyscallSucceeds());
+
+  // Regular dup once.
+  FileDescriptor nfd = ASSERT_NO_ERRNO_AND_VALUE(fd.Dup());
+  ASSERT_NE(fd.get(), nfd.get());
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
+
+  // Dup over the file above, check that it has no CLOEXEC.
+  nfd = ASSERT_NO_ERRNO_AND_VALUE(Dup3(fd, nfd.release(), 0));
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFD), SyscallSucceedsWithValue(0));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFL), SyscallSucceedsWithValue(flags));
+
+  // Dup over the file again, check that it does not CLOEXEC.
+  nfd = ASSERT_NO_ERRNO_AND_VALUE(Dup3(fd, nfd.release(), O_CLOEXEC));
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFD), SyscallSucceedsWithValue(FD_CLOEXEC));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFL), SyscallSucceedsWithValue(flags));
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/fadvise64.cc b/test/syscalls/linux/fadvise64.cc
index 2af7aa6d9..ac24c4066 100644
--- a/test/syscalls/linux/fadvise64.cc
+++ b/test/syscalls/linux/fadvise64.cc
@@ -45,6 +45,17 @@ TEST(FAdvise64Test, Basic) {
               SyscallSucceeds());
 }
 
+TEST(FAdvise64Test, FAdvise64WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const auto fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  ASSERT_THAT(syscall(__NR_fadvise64, fd.get(), 0, 10, POSIX_FADV_NORMAL),
+              SyscallFailsWithErrno(EBADF));
+  ASSERT_THAT(syscall(__NR_fadvise64, fd.get(), 0, 10, POSIX_FADV_NORMAL),
+              SyscallFailsWithErrno(EBADF));
+}
+
 TEST(FAdvise64Test, InvalidArgs) {
   auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   const auto fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_RDONLY));
diff --git a/test/syscalls/linux/fallocate.cc b/test/syscalls/linux/fallocate.cc
index edd23e063..5c839447e 100644
--- a/test/syscalls/linux/fallocate.cc
+++ b/test/syscalls/linux/fallocate.cc
@@ -108,6 +108,13 @@ TEST_F(AllocateTest, FallocateReadonly) {
   EXPECT_THAT(fallocate(fd.get(), 0, 0, 10), SyscallFailsWithErrno(EBADF));
 }
 
+TEST_F(AllocateTest, FallocateWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+  EXPECT_THAT(fallocate(fd.get(), 0, 0, 10), SyscallFailsWithErrno(EBADF));
+}
+
 TEST_F(AllocateTest, FallocatePipe) {
   int pipes[2];
   EXPECT_THAT(pipe(pipes), SyscallSucceeds());
diff --git a/test/syscalls/linux/fchdir.cc b/test/syscalls/linux/fchdir.cc
index 08bcae1e8..c6675802d 100644
--- a/test/syscalls/linux/fchdir.cc
+++ b/test/syscalls/linux/fchdir.cc
@@ -71,6 +71,18 @@ TEST(FchdirTest, NotDir) {
   EXPECT_THAT(close(fd), SyscallSucceeds());
 }
 
+TEST(FchdirTest, FchdirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto temp_dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(temp_dir.path(), O_PATH));
+  ASSERT_THAT(open(temp_dir.path().c_str(), O_DIRECTORY | O_PATH),
+              SyscallSucceeds());
+
+  EXPECT_THAT(fchdir(fd.get()), SyscallSucceeds());
+  // Change CWD to a permanent location as temp dirs will be cleaned up.
+  EXPECT_THAT(chdir("/"), SyscallSucceeds());
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/fcntl.cc b/test/syscalls/linux/fcntl.cc
index 75a5c9f17..4fa6751ff 100644
--- a/test/syscalls/linux/fcntl.cc
+++ b/test/syscalls/linux/fcntl.cc
@@ -207,6 +207,41 @@ PosixErrorOr<Cleanup> SubprocessLock(std::string const& path, bool for_write,
   return std::move(cleanup);
 }
 
+TEST(FcntlTest, FcntlDupWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto f = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(f.path(), O_PATH));
+
+  int new_fd;
+  // Dup the descriptor and make sure it's the same file.
+  EXPECT_THAT(new_fd = fcntl(fd.get(), F_DUPFD, 0), SyscallSucceeds());
+
+  FileDescriptor nfd = FileDescriptor(new_fd);
+  ASSERT_NE(fd.get(), nfd.get());
+  ASSERT_NO_ERRNO(CheckSameFile(fd, nfd));
+  EXPECT_THAT(fcntl(nfd.get(), F_GETFL), SyscallSucceedsWithValue(O_PATH));
+}
+
+TEST(FcntlTest, SetFileStatusFlagWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_PATH));
+
+  EXPECT_THAT(fcntl(fd.get(), F_SETFL, 0), SyscallFailsWithErrno(EBADF));
+}
+
+TEST(FcntlTest, BadFcntlsWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_PATH));
+
+  EXPECT_THAT(fcntl(fd.get(), F_SETOWN, 0), SyscallFailsWithErrno(EBADF));
+  EXPECT_THAT(fcntl(fd.get(), F_GETOWN, 0), SyscallFailsWithErrno(EBADF));
+
+  EXPECT_THAT(fcntl(fd.get(), F_SETOWN_EX, 0), SyscallFailsWithErrno(EBADF));
+  EXPECT_THAT(fcntl(fd.get(), F_GETOWN_EX, 0), SyscallFailsWithErrno(EBADF));
+}
+
 TEST(FcntlTest, SetCloExecBadFD) {
   // Open an eventfd file descriptor with FD_CLOEXEC descriptor flag not set.
   FileDescriptor f = ASSERT_NO_ERRNO_AND_VALUE(NewEventFD(0, 0));
@@ -226,6 +261,32 @@ TEST(FcntlTest, SetCloExec) {
   ASSERT_THAT(fcntl(fd.get(), F_GETFD), SyscallSucceedsWithValue(FD_CLOEXEC));
 }
 
+TEST(FcntlTest, SetCloExecWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  // Open a file descriptor with FD_CLOEXEC descriptor flag not set.
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_PATH));
+  ASSERT_THAT(fcntl(fd.get(), F_GETFD), SyscallSucceedsWithValue(0));
+
+  // Set the FD_CLOEXEC flag.
+  ASSERT_THAT(fcntl(fd.get(), F_SETFD, FD_CLOEXEC), SyscallSucceeds());
+  ASSERT_THAT(fcntl(fd.get(), F_GETFD), SyscallSucceedsWithValue(FD_CLOEXEC));
+}
+
+TEST(FcntlTest, DupFDCloExecWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  // Open a file descriptor with FD_CLOEXEC descriptor flag not set.
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_PATH));
+  int nfd;
+  ASSERT_THAT(nfd = fcntl(fd.get(), F_DUPFD_CLOEXEC, 0), SyscallSucceeds());
+  FileDescriptor dup_fd(nfd);
+
+  // Check for the FD_CLOEXEC flag.
+  ASSERT_THAT(fcntl(dup_fd.get(), F_GETFD),
+              SyscallSucceedsWithValue(FD_CLOEXEC));
+}
+
 TEST(FcntlTest, ClearCloExec) {
   // Open an eventfd file descriptor with FD_CLOEXEC descriptor flag set.
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(NewEventFD(0, EFD_CLOEXEC));
@@ -267,6 +328,22 @@ TEST(FcntlTest, GetAllFlags) {
   EXPECT_EQ(rflags, expected);
 }
 
+// When O_PATH is specified in flags, flag bits other than O_CLOEXEC,
+// O_DIRECTORY, and O_NOFOLLOW are ignored.
+TEST(FcntlTest, GetOpathFlag) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  int flags = O_RDWR | O_DIRECT | O_SYNC | O_NONBLOCK | O_APPEND | O_PATH |
+              O_NOFOLLOW | O_DIRECTORY;
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), flags));
+
+  int expected = O_PATH | O_NOFOLLOW | O_DIRECTORY;
+
+  int rflags;
+  EXPECT_THAT(rflags = fcntl(fd.get(), F_GETFL), SyscallSucceeds());
+  EXPECT_EQ(rflags, expected);
+}
+
 TEST(FcntlTest, SetFlags) {
   TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), 0));
@@ -395,6 +472,22 @@ TEST_F(FcntlLockTest, SetLockBadOpenFlagsRead) {
   EXPECT_THAT(fcntl(fd.get(), F_SETLK, &fl1), SyscallFailsWithErrno(EBADF));
 }
 
+TEST_F(FcntlLockTest, SetLockWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  struct flock fl0;
+  fl0.l_type = F_WRLCK;
+  fl0.l_whence = SEEK_SET;
+  fl0.l_start = 0;
+  fl0.l_len = 0;  // Lock all file
+
+  // Expect that setting a write lock using a Opath file descriptor
+  // won't work.
+  EXPECT_THAT(fcntl(fd.get(), F_SETLK, &fl0), SyscallFailsWithErrno(EBADF));
+}
+
 TEST_F(FcntlLockTest, SetLockUnlockOnNothing) {
   auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   FileDescriptor fd =
diff --git a/test/syscalls/linux/getdents.cc b/test/syscalls/linux/getdents.cc
index 93c692dd6..2f2b14037 100644
--- a/test/syscalls/linux/getdents.cc
+++ b/test/syscalls/linux/getdents.cc
@@ -429,6 +429,32 @@ TYPED_TEST(GetdentsTest, NotDir) {
               SyscallFailsWithErrno(ENOTDIR));
 }
 
+// Test that getdents returns EBADF when called on an opath file.
+TYPED_TEST(GetdentsTest, OpathFile) {
+  SKIP_IF(IsRunningWithVFS1());
+
+  auto file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  auto fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  typename TestFixture::DirentBufferType dirents(256);
+  EXPECT_THAT(RetryEINTR(syscall)(this->SyscallNum(), fd.get(), dirents.Data(),
+                                  dirents.Size()),
+              SyscallFailsWithErrno(EBADF));
+}
+
+// Test that getdents returns EBADF when called on an opath directory.
+TYPED_TEST(GetdentsTest, OpathDirectory) {
+  SKIP_IF(IsRunningWithVFS1());
+
+  auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  auto fd = ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path(), O_PATH | O_DIRECTORY));
+
+  typename TestFixture::DirentBufferType dirents(256);
+  ASSERT_THAT(RetryEINTR(syscall)(this->SyscallNum(), fd.get(), dirents.Data(),
+                                  dirents.Size()),
+              SyscallFailsWithErrno(EBADF));
+}
+
 // Test that SEEK_SET to 0 causes getdents to re-read the entries.
 TYPED_TEST(GetdentsTest, SeekResetsCursor) {
   // . and .. should be in an otherwise empty directory.
diff --git a/test/syscalls/linux/ioctl.cc b/test/syscalls/linux/ioctl.cc
index b0a07a064..9b16d1558 100644
--- a/test/syscalls/linux/ioctl.cc
+++ b/test/syscalls/linux/ioctl.cc
@@ -76,6 +76,19 @@ TEST_F(IoctlTest, InvalidControlNumber) {
   EXPECT_THAT(ioctl(STDOUT_FILENO, 0), SyscallFailsWithErrno(ENOTTY));
 }
 
+TEST_F(IoctlTest, IoctlWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/null", O_PATH));
+
+  int set = 1;
+  EXPECT_THAT(ioctl(fd.get(), FIONBIO, &set), SyscallFailsWithErrno(EBADF));
+
+  EXPECT_THAT(ioctl(fd.get(), FIONCLEX), SyscallFailsWithErrno(EBADF));
+
+  EXPECT_THAT(ioctl(fd.get(), FIOCLEX), SyscallFailsWithErrno(EBADF));
+}
+
 TEST_F(IoctlTest, FIONBIOSucceeds) {
   EXPECT_FALSE(CheckNonBlocking(fd()));
   int set = 1;
diff --git a/test/syscalls/linux/link.cc b/test/syscalls/linux/link.cc
index 544681168..4f9ca1a65 100644
--- a/test/syscalls/linux/link.cc
+++ b/test/syscalls/linux/link.cc
@@ -50,6 +50,8 @@ bool IsSameFile(const std::string& f1, const std::string& f2) {
   return stat1.st_dev == stat2.st_dev && stat1.st_ino == stat2.st_ino;
 }
 
+// TODO(b/178640646): Add test for linkat with AT_EMPTY_PATH
+
 TEST(LinkTest, CanCreateLinkFile) {
   auto oldfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   const std::string newname = NewTempAbsPath();
@@ -235,6 +237,59 @@ TEST(LinkTest, AbsPathsWithNonDirFDs) {
               SyscallSucceeds());
 }
 
+TEST(LinkTest, NewDirFDWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto oldfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const std::string newname_parent = NewTempAbsPath();
+  const std::string newname_base = "child";
+  const std::string newname = JoinPath(newname_parent, newname_base);
+
+  // Create newname_parent directory, and get an FD.
+  EXPECT_THAT(mkdir(newname_parent.c_str(), 0777), SyscallSucceeds());
+  const FileDescriptor newname_parent_fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(newname_parent, O_DIRECTORY | O_PATH));
+
+  // Link newname to oldfile, using newname_parent_fd.
+  EXPECT_THAT(linkat(AT_FDCWD, oldfile.path().c_str(), newname_parent_fd.get(),
+                     newname.c_str(), 0),
+              SyscallSucceeds());
+
+  EXPECT_TRUE(IsSameFile(oldfile.path(), newname));
+}
+
+TEST(LinkTest, RelPathsNonDirFDsWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto oldfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+
+  // Create a file that will be passed as the directory fd for old/new names.
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor file_fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_PATH));
+
+  // Using file_fd as olddirfd will fail.
+  EXPECT_THAT(linkat(file_fd.get(), "foo", AT_FDCWD, "bar", 0),
+              SyscallFailsWithErrno(ENOTDIR));
+
+  // Using file_fd as newdirfd will fail.
+  EXPECT_THAT(linkat(AT_FDCWD, oldfile.path().c_str(), file_fd.get(), "bar", 0),
+              SyscallFailsWithErrno(ENOTDIR));
+}
+
+TEST(LinkTest, AbsPathsNonDirFDsWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+
+  auto oldfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const std::string newname = NewTempAbsPath();
+
+  // Create a file that will be passed as the directory fd for old/new names.
+  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor file_fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_PATH));
+
+  // Using file_fd as the dirfds is OK as long as paths are absolute.
+  EXPECT_THAT(linkat(file_fd.get(), oldfile.path().c_str(), file_fd.get(),
+                     newname.c_str(), 0),
+              SyscallSucceeds());
+}
+
 TEST(LinkTest, LinkDoesNotFollowSymlinks) {
   // Create oldfile, and oldsymlink which points to it.
   auto oldfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
diff --git a/test/syscalls/linux/mmap.cc b/test/syscalls/linux/mmap.cc
index 83546830d..93a6d9cde 100644
--- a/test/syscalls/linux/mmap.cc
+++ b/test/syscalls/linux/mmap.cc
@@ -930,6 +930,18 @@ TEST_F(MMapFileTest, WriteSharedOnReadOnlyFd) {
       SyscallFailsWithErrno(EACCES));
 }
 
+// Mmap not allowed on O_PATH FDs.
+TEST_F(MMapFileTest, MmapFileWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  uintptr_t addr;
+  EXPECT_THAT(addr = Map(0, kPageSize, PROT_READ, MAP_PRIVATE, fd.get(), 0),
+              SyscallFailsWithErrno(EBADF));
+}
+
 // The FD must be readable.
 TEST_P(MMapFileParamTest, WriteOnlyFd) {
   const FileDescriptor fd =
diff --git a/test/syscalls/linux/open.cc b/test/syscalls/linux/open.cc
index fcd162ca2..733b17834 100644
--- a/test/syscalls/linux/open.cc
+++ b/test/syscalls/linux/open.cc
@@ -45,7 +45,7 @@ namespace {
 // * O_CREAT
 // * O_DIRECTORY
 // * O_NOFOLLOW
-// * O_PATH <- Will we ever support this?
+// * O_PATH
 //
 // Special operations on open:
 // * O_EXCL
@@ -517,6 +517,26 @@ TEST_F(OpenTest, OpenWithStrangeFlags) {
   EXPECT_THAT(read(fd.get(), &c, 1), SyscallFailsWithErrno(EBADF));
 }
 
+TEST_F(OpenTest, OpenWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false));
+  ASSERT_NO_ERRNO(SetCapability(CAP_DAC_READ_SEARCH, false));
+  const DisableSave ds;  // Permissions are dropped.
+  std::string path = NewTempAbsPath();
+
+  // Create a file without user permissions.
+  const FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(
+      Open(path.c_str(), O_CREAT | O_TRUNC | O_WRONLY, 055));
+
+  // Cannot open file as read only because we are owner and have no permissions
+  // set.
+  EXPECT_THAT(open(path.c_str(), O_RDONLY), SyscallFailsWithErrno(EACCES));
+
+  // Can open file with O_PATH because don't need permissions on the object when
+  // opening with O_PATH.
+  ASSERT_NO_ERRNO(Open(path, O_PATH));
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/pread64.cc b/test/syscalls/linux/pread64.cc
index bcdbbb044..c74990ba1 100644
--- a/test/syscalls/linux/pread64.cc
+++ b/test/syscalls/linux/pread64.cc
@@ -77,6 +77,16 @@ TEST_F(Pread64Test, WriteOnlyNotReadable) {
   EXPECT_THAT(pread64(fd.get(), buf, 1024, 0), SyscallFailsWithErrno(EBADF));
 }
 
+TEST_F(Pread64Test, Pread64WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  char buf[1024];
+  EXPECT_THAT(pread64(fd.get(), buf, 1024, 0), SyscallFailsWithErrno(EBADF));
+}
+
 TEST_F(Pread64Test, DirNotReadable) {
   const FileDescriptor fd =
       ASSERT_NO_ERRNO_AND_VALUE(Open(GetAbsoluteTestTmpdir(), O_RDONLY));
diff --git a/test/syscalls/linux/preadv.cc b/test/syscalls/linux/preadv.cc
index 5b0743fe9..1c40f0915 100644
--- a/test/syscalls/linux/preadv.cc
+++ b/test/syscalls/linux/preadv.cc
@@ -89,6 +89,20 @@ TEST(PreadvTest, MMConcurrencyStress) {
   // The test passes if it neither deadlocks nor crashes the OS.
 }
 
+// This test calls preadv with an O_PATH fd.
+TEST(PreadvTest, PreadvWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  struct iovec iov;
+  iov.iov_base = nullptr;
+  iov.iov_len = 0;
+
+  EXPECT_THAT(preadv(fd.get(), &iov, 1, 0), SyscallFailsWithErrno(EBADF));
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/preadv2.cc b/test/syscalls/linux/preadv2.cc
index 4a9acd7ae..cb58719c4 100644
--- a/test/syscalls/linux/preadv2.cc
+++ b/test/syscalls/linux/preadv2.cc
@@ -226,6 +226,24 @@ TEST(Preadv2Test, TestUnreadableFile) {
               SyscallFailsWithErrno(EBADF));
 }
 
+// This test calls preadv2 with a file opened with O_PATH.
+TEST(Preadv2Test, Preadv2WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  SKIP_IF(preadv2(-1, nullptr, 0, 0, 0) < 0 && errno == ENOSYS);
+
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  auto iov = absl::make_unique<struct iovec[]>(1);
+  iov[0].iov_base = nullptr;
+  iov[0].iov_len = 0;
+
+  EXPECT_THAT(preadv2(fd.get(), iov.get(), /*iovcnt=*/1, /*offset=*/0,
+                      /*flags=*/0),
+              SyscallFailsWithErrno(EBADF));
+}
+
 // Calling preadv2 with a non-negative offset calls preadv.  Calling preadv with
 // an unseekable file is not allowed. A pipe is used for an unseekable file.
 TEST(Preadv2Test, TestUnseekableFileInvalid) {
diff --git a/test/syscalls/linux/pwrite64.cc b/test/syscalls/linux/pwrite64.cc
index e69794910..1b2f25363 100644
--- a/test/syscalls/linux/pwrite64.cc
+++ b/test/syscalls/linux/pwrite64.cc
@@ -77,6 +77,17 @@ TEST_F(Pwrite64, Overflow) {
   EXPECT_THAT(close(fd), SyscallSucceeds());
 }
 
+TEST_F(Pwrite64, Pwrite64WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  std::vector<char> buf(1);
+  EXPECT_THAT(PwriteFd(fd.get(), buf.data(), 1, 0),
+              SyscallFailsWithErrno(EBADF));
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/pwritev2.cc b/test/syscalls/linux/pwritev2.cc
index 63b686c62..00aed61b4 100644
--- a/test/syscalls/linux/pwritev2.cc
+++ b/test/syscalls/linux/pwritev2.cc
@@ -283,6 +283,23 @@ TEST(Pwritev2Test, ReadOnlyFile) {
               SyscallFailsWithErrno(EBADF));
 }
 
+TEST(Pwritev2Test, Pwritev2WithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  SKIP_IF(pwritev2(-1, nullptr, 0, 0, 0) < 0 && errno == ENOSYS);
+
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  char buf[16];
+  struct iovec iov;
+  iov.iov_base = buf;
+  iov.iov_len = sizeof(buf);
+
+  EXPECT_THAT(pwritev2(fd.get(), &iov, /*iovcnt=*/1, /*offset=*/0, /*flags=*/0),
+              SyscallFailsWithErrno(EBADF));
+}
+
 // This test calls pwritev2 with an invalid flag.
 TEST(Pwritev2Test, InvalidFlag) {
   SKIP_IF(pwritev2(-1, nullptr, 0, 0, 0) < 0 && errno == ENOSYS);
diff --git a/test/syscalls/linux/read.cc b/test/syscalls/linux/read.cc
index 2633ba31b..98d5e432d 100644
--- a/test/syscalls/linux/read.cc
+++ b/test/syscalls/linux/read.cc
@@ -112,6 +112,15 @@ TEST_F(ReadTest, ReadDirectoryFails) {
   EXPECT_THAT(ReadFd(file.get(), buf.data(), 1), SyscallFailsWithErrno(EISDIR));
 }
 
+TEST_F(ReadTest, ReadWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+  std::vector<char> buf(1);
+  EXPECT_THAT(ReadFd(fd.get(), buf.data(), 1), SyscallFailsWithErrno(EBADF));
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/readv.cc b/test/syscalls/linux/readv.cc
index baaf9f757..86808d255 100644
--- a/test/syscalls/linux/readv.cc
+++ b/test/syscalls/linux/readv.cc
@@ -251,6 +251,20 @@ TEST_F(ReadvTest, IovecOutsideTaskAddressRangeInNonemptyArray) {
               SyscallFailsWithErrno(EFAULT));
 }
 
+TEST_F(ReadvTest, ReadvWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  char buffer[1024];
+  struct iovec iov[1];
+  iov[0].iov_base = buffer;
+  iov[0].iov_len = 1024;
+
+  TempPath tmpfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(tmpfile.path().c_str(), O_PATH));
+
+  ASSERT_THAT(readv(fd.get(), iov, 1), SyscallFailsWithErrno(EBADF));
+}
+
 // This test depends on the maximum extent of a single readv() syscall, so
 // we can't tolerate interruption from saving.
 TEST(ReadvTestNoFixture, TruncatedAtMax_NoRandomSave) {
diff --git a/test/syscalls/linux/stat.cc b/test/syscalls/linux/stat.cc
index 6e7142a42..72f888659 100644
--- a/test/syscalls/linux/stat.cc
+++ b/test/syscalls/linux/stat.cc
@@ -221,6 +221,43 @@ TEST_F(StatTest, TrailingSlashNotCleanedReturnsENOTDIR) {
   EXPECT_THAT(lstat(bad_path.c_str(), &buf), SyscallFailsWithErrno(ENOTDIR));
 }
 
+TEST_F(StatTest, FstatFileWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  struct stat st;
+  TempPath tmpfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(tmpfile.path().c_str(), O_PATH));
+
+  // Stat the directory.
+  ASSERT_THAT(fstat(fd.get(), &st), SyscallSucceeds());
+}
+
+TEST_F(StatTest, FstatDirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  struct stat st;
+  TempPath tmpdir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  FileDescriptor dirfd = ASSERT_NO_ERRNO_AND_VALUE(
+      Open(tmpdir.path().c_str(), O_PATH | O_DIRECTORY));
+
+  // Stat the directory.
+  ASSERT_THAT(fstat(dirfd.get(), &st), SyscallSucceeds());
+}
+
+// fstatat with an O_PATH fd
+TEST_F(StatTest, FstatatDirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath tmpdir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  FileDescriptor dirfd = ASSERT_NO_ERRNO_AND_VALUE(
+      Open(tmpdir.path().c_str(), O_PATH | O_DIRECTORY));
+  TempPath tmpfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+
+  struct stat st = {};
+  EXPECT_THAT(fstatat(dirfd.get(), tmpfile.path().c_str(), &st, 0),
+              SyscallSucceeds());
+  EXPECT_FALSE(S_ISDIR(st.st_mode));
+  EXPECT_TRUE(S_ISREG(st.st_mode));
+}
+
 // Test fstatating a symlink directory.
 TEST_F(StatTest, FstatatSymlinkDir) {
   // Create a directory and symlink to it.
diff --git a/test/syscalls/linux/statfs.cc b/test/syscalls/linux/statfs.cc
index f0fb166bd..d4ea8e026 100644
--- a/test/syscalls/linux/statfs.cc
+++ b/test/syscalls/linux/statfs.cc
@@ -64,6 +64,16 @@ TEST(FstatfsTest, InternalTmpfs) {
   EXPECT_THAT(fstatfs(fd.get(), &st), SyscallSucceeds());
 }
 
+TEST(FstatfsTest, CanStatFileWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto temp_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(temp_file.path(), O_PATH));
+
+  struct statfs st;
+  EXPECT_THAT(fstatfs(fd.get(), &st), SyscallSucceeds());
+}
+
 TEST(FstatfsTest, InternalDevShm) {
   auto temp_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
   const FileDescriptor fd =
diff --git a/test/syscalls/linux/symlink.cc b/test/syscalls/linux/symlink.cc
index 4d9eba7f0..ea219a091 100644
--- a/test/syscalls/linux/symlink.cc
+++ b/test/syscalls/linux/symlink.cc
@@ -269,6 +269,36 @@ TEST(SymlinkTest, SymlinkAtDegradedPermissions_NoRandomSave) {
   EXPECT_THAT(close(dirfd), SyscallSucceeds());
 }
 
+TEST(SymlinkTest, SymlinkAtDirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  const std::string filepath = NewTempAbsPathInDir(dir.path());
+  const std::string base = std::string(Basename(filepath));
+  FileDescriptor dirfd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path().c_str(), O_DIRECTORY | O_PATH));
+
+  EXPECT_THAT(symlinkat("/dangling", dirfd.get(), base.c_str()),
+              SyscallSucceeds());
+}
+
+TEST(SymlinkTest, ReadlinkAtDirWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto dir = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
+  const std::string filepath = NewTempAbsPathInDir(dir.path());
+  const std::string base = std::string(Basename(filepath));
+  ASSERT_THAT(symlink("/dangling", filepath.c_str()), SyscallSucceeds());
+
+  FileDescriptor dirfd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(dir.path().c_str(), O_DIRECTORY | O_PATH));
+
+  std::vector<char> buf(1024);
+  int linksize;
+  EXPECT_THAT(
+      linksize = readlinkat(dirfd.get(), base.c_str(), buf.data(), 1024),
+      SyscallSucceeds());
+  EXPECT_EQ(0, strncmp("/dangling", buf.data(), linksize));
+}
+
 TEST(SymlinkTest, ReadlinkAtDegradedPermissions_NoRandomSave) {
   // Drop capabilities that allow us to override file and directory permissions.
   ASSERT_NO_ERRNO(SetCapability(CAP_DAC_OVERRIDE, false));
diff --git a/test/syscalls/linux/sync.cc b/test/syscalls/linux/sync.cc
index 8aa2525a9..84a2c4ed7 100644
--- a/test/syscalls/linux/sync.cc
+++ b/test/syscalls/linux/sync.cc
@@ -49,10 +49,20 @@ TEST(SyncTest, SyncFromPipe) {
   EXPECT_THAT(close(pipes[1]), SyscallSucceeds());
 }
 
-TEST(SyncTest, CannotSyncFileSytemAtBadFd) {
+TEST(SyncTest, CannotSyncFileSystemAtBadFd) {
   EXPECT_THAT(syncfs(-1), SyscallFailsWithErrno(EBADF));
 }
 
+TEST(SyncTest, CannotSyncFileSystemAtOpathFD) {
+  SKIP_IF(IsRunningWithVFS1());
+
+  const TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileWith(
+      GetAbsoluteTestTmpdir(), "", TempPath::kDefaultFileMode));
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_PATH));
+
+  EXPECT_THAT(syncfs(fd.get()), SyscallFailsWithErrno(EBADF));
+}
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/truncate.cc b/test/syscalls/linux/truncate.cc
index bfc95ed38..17832c47d 100644
--- a/test/syscalls/linux/truncate.cc
+++ b/test/syscalls/linux/truncate.cc
@@ -196,6 +196,16 @@ TEST(TruncateTest, FtruncateNonWriteable) {
   EXPECT_THAT(ftruncate(fd.get(), 0), SyscallFailsWithErrno(EINVAL));
 }
 
+TEST(TruncateTest, FtruncateWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  auto temp_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileWith(
+      GetAbsoluteTestTmpdir(), absl::string_view(), 0555 /* mode */));
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(temp_file.path(), O_PATH));
+  EXPECT_THAT(ftruncate(fd.get(), 0), AnyOf(SyscallFailsWithErrno(EBADF),
+                                            SyscallFailsWithErrno(EINVAL)));
+}
+
 // ftruncate(2) should succeed as long as the file descriptor is writeable,
 // regardless of whether the file permissions allow writing.
 TEST(TruncateTest, FtruncateWithoutWritePermission_NoRandomSave) {
diff --git a/test/syscalls/linux/write.cc b/test/syscalls/linux/write.cc
index 77bcfbb8a..740992d0a 100644
--- a/test/syscalls/linux/write.cc
+++ b/test/syscalls/linux/write.cc
@@ -218,6 +218,44 @@ TEST_F(WriteTest, PwriteNoChangeOffset) {
   EXPECT_THAT(lseek(fd, 0, SEEK_CUR), SyscallSucceedsWithValue(bytes_total));
 }
 
+TEST_F(WriteTest, WriteWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath tmpfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor f =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(tmpfile.path().c_str(), O_PATH));
+  int fd = f.get();
+
+  EXPECT_THAT(WriteBytes(fd, 1024), SyscallFailsWithErrno(EBADF));
+}
+
+TEST_F(WriteTest, WritevWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath tmpfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor f =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(tmpfile.path().c_str(), O_PATH));
+  int fd = f.get();
+
+  char buf[16];
+  struct iovec iov;
+  iov.iov_base = buf;
+  iov.iov_len = sizeof(buf);
+
+  EXPECT_THAT(writev(fd, &iov, /*__count=*/1), SyscallFailsWithErrno(EBADF));
+}
+
+TEST_F(WriteTest, PwriteWithOpath) {
+  SKIP_IF(IsRunningWithVFS1());
+  TempPath tmpfile = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor f =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(tmpfile.path().c_str(), O_PATH));
+  int fd = f.get();
+
+  const std::string data = "hello world\n";
+
+  EXPECT_THAT(pwrite(fd, data.data(), data.size(), 0),
+              SyscallFailsWithErrno(EBADF));
+}
+
 }  // namespace
 
 }  // namespace testing
diff --git a/test/syscalls/linux/xattr.cc b/test/syscalls/linux/xattr.cc
index bd3f829c4..a953a55fe 100644
--- a/test/syscalls/linux/xattr.cc
+++ b/test/syscalls/linux/xattr.cc
@@ -607,6 +607,27 @@ TEST_F(XattrTest, XattrWithFD) {
   EXPECT_THAT(fremovexattr(fd.get(), name), SyscallSucceeds());
 }
 
+TEST_F(XattrTest, XattrWithOPath) {
+  SKIP_IF(IsRunningWithVFS1());
+  const FileDescriptor fd =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(test_file_name_.c_str(), O_PATH));
+  const char name[] = "user.test";
+  int val = 1234;
+  size_t size = sizeof(val);
+  EXPECT_THAT(fsetxattr(fd.get(), name, &val, size, /*flags=*/0),
+              SyscallFailsWithErrno(EBADF));
+
+  int buf;
+  EXPECT_THAT(fgetxattr(fd.get(), name, &buf, size),
+              SyscallFailsWithErrno(EBADF));
+
+  char list[sizeof(name)];
+  EXPECT_THAT(flistxattr(fd.get(), list, sizeof(list)),
+              SyscallFailsWithErrno(EBADF));
+
+  EXPECT_THAT(fremovexattr(fd.get(), name), SyscallFailsWithErrno(EBADF));
+}
+
 TEST_F(XattrTest, TrustedNamespaceWithCapSysAdmin) {
   // Trusted namespace not supported in VFS1.
   SKIP_IF(IsRunningWithVFS1());
diff --git a/test/util/fs_util.cc b/test/util/fs_util.cc
index b16055dd8..5f1ce0d8a 100644
--- a/test/util/fs_util.cc
+++ b/test/util/fs_util.cc
@@ -663,5 +663,21 @@ PosixErrorOr<bool> IsOverlayfs(const std::string& path) {
   return stat.f_type == OVERLAYFS_SUPER_MAGIC;
 }
 
+PosixError CheckSameFile(const FileDescriptor& fd1, const FileDescriptor& fd2) {
+  struct stat stat_result1, stat_result2;
+  int res = fstat(fd1.get(), &stat_result1);
+  if (res < 0) {
+    return PosixError(errno, absl::StrCat("fstat ", fd1.get()));
+  }
+
+  res = fstat(fd2.get(), &stat_result2);
+  if (res < 0) {
+    return PosixError(errno, absl::StrCat("fstat ", fd2.get()));
+  }
+  EXPECT_EQ(stat_result1.st_dev, stat_result2.st_dev);
+  EXPECT_EQ(stat_result1.st_ino, stat_result2.st_ino);
+
+  return NoError();
+}
 }  // namespace testing
 }  // namespace gvisor
diff --git a/test/util/fs_util.h b/test/util/fs_util.h
index c99cf5eb7..2190c3bca 100644
--- a/test/util/fs_util.h
+++ b/test/util/fs_util.h
@@ -191,6 +191,8 @@ PosixErrorOr<bool> IsTmpfs(const std::string& path);
 // IsOverlayfs returns true if the file at path is backed by overlayfs.
 PosixErrorOr<bool> IsOverlayfs(const std::string& path);
 
+PosixError CheckSameFile(const FileDescriptor& fd1, const FileDescriptor& fd2);
+
 namespace internal {
 // Not part of the public API.
 std::string JoinPathImpl(std::initializer_list<absl::string_view> paths);