Implement FUSE_MKNOD

Fixes #3492

5 files changed, 182 insertions, 0 deletions

diff --git a/pkg/abi/linux/fuse.go b/pkg/abi/linux/fuse.go
index a1b2a2abf..97d960096 100644
--- a/pkg/abi/linux/fuse.go
+++ b/pkg/abi/linux/fuse.go
@@ -413,3 +413,46 @@ type FUSEReleaseIn struct {
 	// LockOwner is the id of the lock owner if there is one.
 	LockOwner uint64
 }
+
+// FUSEMknodMeta contains all the static fields of FUSEMknodIn,
+// which is used for FUSE_MKNOD.
+//
+// +marshal
+type FUSEMknodMeta struct {
+	// Mode of the inode to create.
+	Mode uint32
+
+	// Rdev encodes device major and minor information.
+	Rdev uint32
+
+	// Umask is the current file mode creation mask.
+	Umask uint32
+
+	_ uint32
+}
+
+// FUSEMknodIn contains all the arguments sent by the kernel
+// to the daemon, to create a new file node.
+//
+// Dynamically-sized objects cannot be marshalled.
+type FUSEMknodIn struct {
+	marshal.StubMarshallable
+
+	// MknodMeta contains mode, rdev and umash field for FUSE_MKNODS.
+	MknodMeta FUSEMknodMeta
+
+	// Name is the name of the node to create.
+	Name string
+}
+
+// MarshalUnsafe serializes r.MknodMeta and r.Name to the dst buffer.
+func (r *FUSEMknodIn) MarshalUnsafe(buf []byte) {
+	r.MknodMeta.MarshalUnsafe(buf[:r.MknodMeta.SizeBytes()])
+	copy(buf[r.MknodMeta.SizeBytes():], r.Name)
+}
+
+// SizeBytes is the size of the memory representation of FUSEMknodIn.
+// 1 extra byte for null-terminated string.
+func (r *FUSEMknodIn) SizeBytes() int {
+	return r.MknodMeta.SizeBytes() + len(r.Name) + 1
+}
diff --git a/pkg/sentry/fsimpl/fuse/fusefs.go b/pkg/sentry/fsimpl/fuse/fusefs.go
index b5f05b80b..5cef0b94f 100644
--- a/pkg/sentry/fsimpl/fuse/fusefs.go
+++ b/pkg/sentry/fsimpl/fuse/fusefs.go
@@ -349,6 +349,19 @@ func (inode) Valid(ctx context.Context) bool {
 	return true
 }
 
+// NewNode implements kernfs.Inode.NewNode.
+func (i *inode) NewNode(ctx context.Context, name string, opts vfs.MknodOptions) (*vfs.Dentry, error) {
+	in := linux.FUSEMknodIn{
+		MknodMeta: linux.FUSEMknodMeta{
+			Mode:  uint32(opts.Mode),
+			Rdev:  linux.MakeDeviceID(uint16(opts.DevMajor), opts.DevMinor),
+			Umask: uint32(kernel.TaskFromContext(ctx).FSContext().Umask()),
+		},
+		Name: name,
+	}
+	return i.newEntry(ctx, name, opts.Mode.FileType(), linux.FUSE_MKNOD, &in)
+}
+
 // newEntry calls FUSE server for entry creation and allocates corresponding entry according to response.
 // Shared by FUSE_MKNOD, FUSE_MKDIR, FUSE_SYMLINK, FUSE_LINK and FUSE_LOOKUP.
 func (i *inode) newEntry(ctx context.Context, name string, fileType linux.FileMode, opcode linux.FUSEOpcode, payload marshal.Marshallable) (*vfs.Dentry, error) {
diff --git a/test/fuse/BUILD b/test/fuse/BUILD
index 53cbadb3c..ff2948eb3 100644
--- a/test/fuse/BUILD
+++ b/test/fuse/BUILD
@@ -16,3 +16,8 @@ syscall_test(
     fuse = "True",
     test = "//test/fuse/linux:release_test",
 )
+
+syscall_test(
+    fuse = "True",
+    test = "//test/fuse/linux:mknod_test",
+)
diff --git a/test/fuse/linux/BUILD b/test/fuse/linux/BUILD
index abee1a33c..c0f917606 100644
--- a/test/fuse/linux/BUILD
+++ b/test/fuse/linux/BUILD
@@ -44,6 +44,20 @@ cc_binary(
     ],
 )
 
+cc_binary(
+    name = "mknod_test",
+    testonly = 1,
+    srcs = ["mknod_test.cc"],
+    deps = [
+        gtest,
+        ":fuse_base",
+        "//test/util:fuse_util",
+        "//test/util:temp_umask",
+        "//test/util:test_main",
+        "//test/util:test_util",
+    ],
+)
+
 cc_library(
     name = "fuse_base",
     testonly = 1,
diff --git a/test/fuse/linux/mknod_test.cc b/test/fuse/linux/mknod_test.cc
new file mode 100644
index 000000000..74c74d76b
--- /dev/null
+++ b/test/fuse/linux/mknod_test.cc
@@ -0,0 +1,107 @@
+// Copyright 2020 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 <errno.h>
+#include <fcntl.h>
+#include <linux/fuse.h>
+#include <sys/stat.h>
+#include <sys/statfs.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <string>
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "test/fuse/linux/fuse_base.h"
+#include "test/util/fuse_util.h"
+#include "test/util/temp_umask.h"
+#include "test/util/test_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+class MknodTest : public FuseTest {
+ protected:
+  const std::string test_file_ = "test_file";
+  const mode_t perms_ = S_IRWXU | S_IRWXG | S_IRWXO;
+};
+
+TEST_F(MknodTest, RegularFile) {
+  const std::string test_file_path =
+      JoinPath(mount_point_.path().c_str(), test_file_);
+  const mode_t new_umask = 0077;
+
+  struct fuse_out_header out_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_entry_out),
+  };
+  struct fuse_entry_out out_payload = DefaultEntryOut(S_IFREG | perms_, 5);
+  auto iov_out = FuseGenerateIovecs(out_header, out_payload);
+  SetServerResponse(FUSE_MKNOD, iov_out);
+  TempUmask mask(new_umask);
+  ASSERT_THAT(mknod(test_file_path.c_str(), perms_, 0), SyscallSucceeds());
+
+  struct fuse_in_header in_header;
+  struct fuse_mknod_in in_payload;
+  std::vector<char> actual_file(test_file_.length() + 1);
+  auto iov_in = FuseGenerateIovecs(in_header, in_payload, actual_file);
+  GetServerActualRequest(iov_in);
+
+  EXPECT_EQ(in_header.len,
+            sizeof(in_header) + sizeof(in_payload) + test_file_.length() + 1);
+  EXPECT_EQ(in_header.opcode, FUSE_MKNOD);
+  EXPECT_EQ(in_payload.mode & 0777, perms_ & ~new_umask);
+  EXPECT_EQ(in_payload.umask, new_umask);
+  EXPECT_EQ(in_payload.rdev, 0);
+  EXPECT_EQ(std::string(actual_file.data()), test_file_);
+}
+
+TEST_F(MknodTest, FileTypeError) {
+  const std::string test_file_path =
+      JoinPath(mount_point_.path().c_str(), test_file_);
+
+  struct fuse_out_header out_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_entry_out),
+  };
+  // server return directory instead of regular file should cause an error.
+  struct fuse_entry_out out_payload = DefaultEntryOut(S_IFDIR | perms_, 5);
+  auto iov_out = FuseGenerateIovecs(out_header, out_payload);
+  SetServerResponse(FUSE_MKNOD, iov_out);
+  ASSERT_THAT(mknod(test_file_path.c_str(), perms_, 0),
+              SyscallFailsWithErrno(EIO));
+  SkipServerActualRequest();
+}
+
+TEST_F(MknodTest, NodeIDError) {
+  const std::string test_file_path =
+      JoinPath(mount_point_.path().c_str(), test_file_);
+
+  struct fuse_out_header out_header = {
+      .len = sizeof(struct fuse_out_header) + sizeof(struct fuse_entry_out),
+  };
+  struct fuse_entry_out out_payload =
+      DefaultEntryOut(S_IFREG | perms_, FUSE_ROOT_ID);
+  auto iov_out = FuseGenerateIovecs(out_header, out_payload);
+  SetServerResponse(FUSE_MKNOD, iov_out);
+  ASSERT_THAT(mknod(test_file_path.c_str(), perms_, 0),
+              SyscallFailsWithErrno(EIO));
+  SkipServerActualRequest();
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor