Merge pull request #2931 from ridwanmsharif:ridwanmsharif/fuse-char-device

PiperOrigin-RevId: 318511615

6 files changed, 140 insertions, 0 deletions

diff --git a/pkg/abi/linux/dev.go b/pkg/abi/linux/dev.go
index fa3ae5f18..192e2093b 100644
--- a/pkg/abi/linux/dev.go
+++ b/pkg/abi/linux/dev.go
@@ -46,6 +46,10 @@ const (
 	// TTYAUX_MAJOR is the major device number for alternate TTY devices.
 	TTYAUX_MAJOR = 5
 
+	// MISC_MAJOR is the major device number for non-serial mice, misc feature
+	// devices.
+	MISC_MAJOR = 10
+
 	// UNIX98_PTY_MASTER_MAJOR is the initial major device number for
 	// Unix98 PTY masters.
 	UNIX98_PTY_MASTER_MAJOR = 128
diff --git a/pkg/sentry/fsimpl/fuse/BUILD b/pkg/sentry/fsimpl/fuse/BUILD
new file mode 100644
index 000000000..41567967d
--- /dev/null
+++ b/pkg/sentry/fsimpl/fuse/BUILD
@@ -0,0 +1,19 @@
+load("//tools:defs.bzl", "go_library")
+
+licenses(["notice"])
+
+go_library(
+    name = "fuse",
+    srcs = [
+        "dev.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/sentry/fsimpl/devtmpfs",
+        "//pkg/sentry/vfs",
+        "//pkg/syserror",
+        "//pkg/usermem",
+    ],
+)
diff --git a/pkg/sentry/fsimpl/fuse/dev.go b/pkg/sentry/fsimpl/fuse/dev.go
new file mode 100644
index 000000000..f6a67d005
--- /dev/null
+++ b/pkg/sentry/fsimpl/fuse/dev.go
@@ -0,0 +1,100 @@
+// 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.
+
+package fuse
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/devtmpfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+const fuseDevMinor = 229
+
+// fuseDevice implements vfs.Device for /dev/fuse.
+type fuseDevice struct{}
+
+// Open implements vfs.Device.Open.
+func (fuseDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	var fd DeviceFD
+	if err := fd.vfsfd.Init(&fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
+		UseDentryMetadata: true,
+	}); err != nil {
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}
+
+// DeviceFD implements vfs.FileDescriptionImpl for /dev/fuse.
+type DeviceFD struct {
+	vfsfd vfs.FileDescription
+	vfs.FileDescriptionDefaultImpl
+	vfs.DentryMetadataFileDescriptionImpl
+	vfs.NoLockFD
+
+	// TODO(gvisor.dev/issue/2987): Add all the data structures needed to enqueue
+	// and deque requests, control synchronization and establish communication
+	// between the FUSE kernel module and the /dev/fuse character device.
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *DeviceFD) Release() {}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *DeviceFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return 0, syserror.ENOSYS
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *DeviceFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	return 0, syserror.ENOSYS
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *DeviceFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	return 0, syserror.ENOSYS
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *DeviceFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	return 0, syserror.ENOSYS
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *DeviceFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	return 0, syserror.ENOSYS
+}
+
+// Register registers the FUSE device with vfsObj.
+func Register(vfsObj *vfs.VirtualFilesystem) error {
+	if err := vfsObj.RegisterDevice(vfs.CharDevice, linux.MISC_MAJOR, fuseDevMinor, fuseDevice{}, &vfs.RegisterDeviceOptions{
+		GroupName: "misc",
+	}); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// CreateDevtmpfsFile creates a device special file in devtmpfs.
+func CreateDevtmpfsFile(ctx context.Context, dev *devtmpfs.Accessor) error {
+	if err := dev.CreateDeviceFile(ctx, "fuse", vfs.CharDevice, linux.MISC_MAJOR, fuseDevMinor, 0666 /* mode */); err != nil {
+		return err
+	}
+
+	return nil
+}
diff --git a/runsc/boot/BUILD b/runsc/boot/BUILD
index 45d7f7d09..aad2a41de 100644
--- a/runsc/boot/BUILD
+++ b/runsc/boot/BUILD
@@ -55,6 +55,7 @@ go_library(
         "//pkg/sentry/fs/user",
         "//pkg/sentry/fsimpl/devpts",
         "//pkg/sentry/fsimpl/devtmpfs",
+        "//pkg/sentry/fsimpl/fuse",
         "//pkg/sentry/fsimpl/gofer",
         "//pkg/sentry/fsimpl/host",
         "//pkg/sentry/fsimpl/overlay",
diff --git a/runsc/boot/vfs.go b/runsc/boot/vfs.go
index 9ba5e9cd9..b68117867 100644
--- a/runsc/boot/vfs.go
+++ b/runsc/boot/vfs.go
@@ -31,6 +31,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs/user"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/devpts"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/devtmpfs"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/fuse"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/gofer"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/overlay"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/proc"
@@ -80,6 +81,10 @@ func registerFilesystems(ctx context.Context, vfsObj *vfs.VirtualFilesystem, cre
 	if err := ttydev.Register(vfsObj); err != nil {
 		return fmt.Errorf("registering ttydev: %w", err)
 	}
+
+	if err := fuse.Register(vfsObj); err != nil {
+		return fmt.Errorf("registering fusedev: %w", err)
+	}
 	if err := tundev.Register(vfsObj); err != nil {
 		return fmt.Errorf("registering tundev: %v", err)
 	}
@@ -101,6 +106,9 @@ func registerFilesystems(ctx context.Context, vfsObj *vfs.VirtualFilesystem, cre
 	if err := tundev.CreateDevtmpfsFiles(ctx, a); err != nil {
 		return fmt.Errorf("creating tundev devtmpfs files: %v", err)
 	}
+	if err := fuse.CreateDevtmpfsFile(ctx, a); err != nil {
+		return fmt.Errorf("creating fusedev devtmpfs files: %w", err)
+	}
 	return nil
 }
 
diff --git a/test/syscalls/linux/dev.cc b/test/syscalls/linux/dev.cc
index 4dd302eed..3c88c4cbd 100644
--- a/test/syscalls/linux/dev.cc
+++ b/test/syscalls/linux/dev.cc
@@ -153,6 +153,14 @@ TEST(DevTest, TTYExists) {
   EXPECT_EQ(statbuf.st_mode, S_IFCHR | 0666);
 }
 
+TEST(DevTest, OpenDevFuse) {
+  // Note(gvisor.dev/issue/3076) This won't work in the sentry until the new
+  // device registration is complete.
+  SKIP_IF(IsRunningWithVFS1() || IsRunningOnGvisor());
+
+  ASSERT_NO_ERRNO_AND_VALUE(Open("/dev/fuse", O_RDONLY));
+}
+
 }  // namespace
 }  // namespace testing