visor/test/syscalls/linux/fuse.cc

// Copyright 2023 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.

#include <fcntl.h>
#include <linux/capability.h>
#include <linux/fuse.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <unistd.h>

#include <cerrno>
#include <cstdint>
#include <cstdlib>
#include <string>
#include <vector>

#include "gmock/gmock.h"
#include "gtest/gtest.h"
#include "absl/strings/str_format.h"
#include "absl/strings/string_view.h"
#include "test/util/file_descriptor.h"
#include "test/util/fs_util.h"
#include "test/util/linux_capability_util.h"
#include "test/util/mount_util.h"
#include "test/util/posix_error.h"
#include "test/util/save_util.h"
#include "test/util/temp_path.h"
#include "test/util/test_util.h"
#include "test/util/thread_util.h"

using ::testing::Ge;

namespace gvisor {
namespace testing {

namespace {

void FuseInit(int fd) {
  alignas(fuse_in_header) char req_buf[FUSE_MIN_READ_BUFFER];
  ASSERT_THAT(read(fd, req_buf, sizeof(req_buf)),
              SyscallSucceedsWithValue(Ge(sizeof(fuse_in_header))));

  fuse_in_header* in_hdr = reinterpret_cast<fuse_in_header*>(req_buf);
  ASSERT_EQ(in_hdr->opcode, FUSE_INIT);

  fuse_out_header out_hdr;
  out_hdr.error = 0;
  out_hdr.unique = in_hdr->unique;
  fuse_init_out out_payload = {};
  out_payload.major = FUSE_KERNEL_VERSION;
  out_payload.minor = FUSE_KERNEL_MINOR_VERSION;
  out_payload.max_readahead = 0;
  out_payload.flags = 0;
  out_payload.congestion_threshold = 0;

  struct iovec iov[] = {
      {.iov_base = &out_hdr, .iov_len = sizeof(out_hdr)},
      {.iov_base = &out_payload, .iov_len = sizeof(out_payload)},
  };
  out_hdr.len = sizeof(out_hdr) + sizeof(out_payload);

  ASSERT_THAT(writev(fd, iov, 2),
              SyscallSucceedsWithValue(sizeof(out_hdr) + sizeof(out_payload)));
}

TEST(FuseTest, RejectBadInit) {
  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
  const FileDescriptor fd =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDWR, 0));

  auto mount_point = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
  auto mount_opts =
      absl::StrFormat("fd=%d,user_id=0,group_id=0,rootmode=40000", fd.get());
  auto mount = ASSERT_NO_ERRNO_AND_VALUE(
      Mount("fuse", mount_point.path(), "fuse", MS_NODEV | MS_NOSUID,
            mount_opts, 0 /* umountflags */));

  // Read the init request so that we have the correct unique ID.
  alignas(fuse_in_header) char req_buf[FUSE_MIN_READ_BUFFER];
  ASSERT_THAT(read(fd.get(), req_buf, sizeof(req_buf)),
              SyscallSucceedsWithValue(Ge(sizeof(fuse_in_header))));

  fuse_out_header resp;
  resp.len = sizeof(resp) - 1;
  resp.error = 0;
  resp.unique = reinterpret_cast<fuse_in_header*>(req_buf)->unique;

  ASSERT_THAT(write(fd.get(), reinterpret_cast<char*>(&resp), sizeof(resp)),
              SyscallFailsWithErrno(EINVAL));
}

TEST(FuseTest, CloneDevice) {
  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
  SKIP_IF(IsRunningWithSaveRestore());

  const FileDescriptor fd1 =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDWR));

  auto mount_point = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
  auto mount_opts =
      absl::StrFormat("fd=%d,user_id=0,group_id=0,rootmode=40000", fd1.get());
  auto mount = ASSERT_NO_ERRNO_AND_VALUE(
      Mount("fuse", mount_point.path(), "fuse", MS_NODEV | MS_NOSUID,
            mount_opts, 0 /* umountflags */));
  FuseInit(fd1.get());

  const FileDescriptor fd2 =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDWR));
  int fd1_num = fd1.get();
  ASSERT_THAT(ioctl(fd2.get(), FUSE_DEV_IOC_CLONE, &fd1_num),
              SyscallSucceeds());

  ScopedThread fuse_server = ScopedThread([&] {
    // Send stat reply from both FUSE servers.
    for (int fd : {fd1.get(), fd2.get()}) {
      // Read the stat request.
      alignas(fuse_in_header) char req_buf[4096 * 4];
      ASSERT_THAT(read(fd, req_buf, sizeof(req_buf)),
                  SyscallSucceedsWithValue(Ge(sizeof(fuse_in_header))));

      fuse_in_header* in_hdr = reinterpret_cast<fuse_in_header*>(req_buf);
      ASSERT_EQ(in_hdr->opcode, FUSE_GETATTR);

      // Send stat reply.
      fuse_out_header out_hdr;
      out_hdr.error = 0;
      out_hdr.unique = in_hdr->unique;
      fuse_attr_out out_payload = {};
      out_payload.attr.mode = S_IFDIR | 0755;
      out_payload.attr.nlink = 1;
      out_payload.attr.uid = 0;
      out_payload.attr.gid = 0;
      out_payload.attr.size = fd;
      out_payload.attr.atime = 0;
      out_payload.attr.mtime = 0;
      out_payload.attr.ctime = 0;

      struct iovec iov[] = {
          {.iov_base = &out_hdr, .iov_len = sizeof(out_hdr)},
          {.iov_base = &out_payload, .iov_len = sizeof(out_payload)},
      };
      out_hdr.len = sizeof(out_hdr) + sizeof(out_payload);

      ASSERT_THAT(
          writev(fd, iov, 2),
          SyscallSucceedsWithValue(sizeof(out_hdr) + sizeof(out_payload)));
    }
  });

  // Check if filesystem is responsive by stat'ing root. Both FUSE servers
  // should be able to respond.
  struct stat st;
  EXPECT_THAT(stat(mount_point.path().c_str(), &st), SyscallSucceeds());
  EXPECT_EQ(st.st_size, fd1.get());
  EXPECT_THAT(stat(mount_point.path().c_str(), &st), SyscallSucceeds());
  EXPECT_EQ(st.st_size, fd2.get());

  fuse_server.Join();
}

TEST(FuseTest, CloneToConnectedDeviceFails) {
  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
  const FileDescriptor fd1 =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDWR));

  auto mount_point = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateDir());
  auto mount_opts =
      absl::StrFormat("fd=%d,user_id=0,group_id=0,rootmode=40000", fd1.get());
  auto mount = ASSERT_NO_ERRNO_AND_VALUE(
      Mount("fuse", mount_point.path(), "fuse", MS_NODEV | MS_NOSUID,
            mount_opts, 0 /* umountflags */));
  FuseInit(fd1.get());

  int fd1_num = fd1.get();
  EXPECT_THAT(ioctl(fd1.get(), FUSE_DEV_IOC_CLONE, &fd1_num),
              SyscallFailsWithErrno(EINVAL));
}

TEST(FuseTest, CloneFromUnconnectedDeviceFails) {
  SKIP_IF(!ASSERT_NO_ERRNO_AND_VALUE(HaveCapability(CAP_SYS_ADMIN)));
  const FileDescriptor fd1 =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDWR));

  const FileDescriptor fd2 =
      ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDWR));

  int fd1_num = fd1.get();
  EXPECT_THAT(ioctl(fd2.get(), FUSE_DEV_IOC_CLONE, &fd1_num),
              SyscallFailsWithErrno(EINVAL));
}

TEST(FuseTest, LookupUpdatesInode) {
  SKIP_IF(absl::NullSafeStringView(getenv("GVISOR_FUSE_TEST")) != "TRUE");
  const std::string kFileData = "May thy knife chip and shatter.\n";
  TempPath path = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileWith(
      GetAbsoluteTestTmpdir(), kFileData, TempPath::kDefaultFileMode));

  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(path.path(), O_RDONLY));
  std::vector<char> buf(kFileData.size());
  ASSERT_THAT(ReadFd(fd.get(), buf.data(), kFileData.size()),
              SyscallSucceedsWithValue(kFileData.size()));

  ASSERT_THAT(unlink(JoinPath("/fuse", Basename(path.path())).c_str()),
              SyscallSucceeds());

  EXPECT_THAT(access(path.path().c_str(), O_RDONLY),
              SyscallFailsWithErrno(ENOENT));
}

}  // namespace
}  // namespace testing
}  // namespace gvisor