Add support for device special files to VFS2 tmpfs.

PiperOrigin-RevId: 291471892

4 files changed, 88 insertions, 25 deletions

diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index 7601c7c04..691476b4f 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -20,6 +20,7 @@ go_library(
     name = "tmpfs",
     srcs = [
         "dentry_list.go",
+        "device_file.go",
         "directory.go",
         "filesystem.go",
         "named_pipe.go",
diff --git a/pkg/sentry/fsimpl/tmpfs/device_file.go b/pkg/sentry/fsimpl/tmpfs/device_file.go
new file mode 100644
index 000000000..84b181b90
--- /dev/null
+++ b/pkg/sentry/fsimpl/tmpfs/device_file.go
@@ -0,0 +1,39 @@
+// 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 tmpfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+type deviceFile struct {
+	inode inode
+	kind  vfs.DeviceKind
+	major uint32
+	minor uint32
+}
+
+func (fs *filesystem) newDeviceFile(creds *auth.Credentials, mode linux.FileMode, kind vfs.DeviceKind, major, minor uint32) *inode {
+	file := &deviceFile{
+		kind:  kind,
+		major: major,
+		minor: minor,
+	}
+	file.inode.init(file, fs, creds, mode)
+	file.inode.nlink = 1 // from parent directory
+	return &file.inode
+}
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index a9f66a42a..d726f03c5 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -228,23 +228,26 @@ func (fs *filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v
 // MknodAt implements vfs.FilesystemImpl.MknodAt.
 func (fs *filesystem) MknodAt(ctx context.Context, rp *vfs.ResolvingPath, opts vfs.MknodOptions) error {
 	return fs.doCreateAt(rp, false /* dir */, func(parent *dentry, name string) error {
+		var childInode *inode
 		switch opts.Mode.FileType() {
 		case 0, linux.S_IFREG:
-			child := fs.newDentry(fs.newRegularFile(rp.Credentials(), opts.Mode))
-			parent.vfsd.InsertChild(&child.vfsd, name)
-			parent.inode.impl.(*directory).childList.PushBack(child)
-			return nil
+			childInode = fs.newRegularFile(rp.Credentials(), opts.Mode)
 		case linux.S_IFIFO:
-			child := fs.newDentry(fs.newNamedPipe(rp.Credentials(), opts.Mode))
-			parent.vfsd.InsertChild(&child.vfsd, name)
-			parent.inode.impl.(*directory).childList.PushBack(child)
-			return nil
-		case linux.S_IFBLK, linux.S_IFCHR, linux.S_IFSOCK:
+			childInode = fs.newNamedPipe(rp.Credentials(), opts.Mode)
+		case linux.S_IFBLK:
+			childInode = fs.newDeviceFile(rp.Credentials(), opts.Mode, vfs.BlockDevice, opts.DevMajor, opts.DevMinor)
+		case linux.S_IFCHR:
+			childInode = fs.newDeviceFile(rp.Credentials(), opts.Mode, vfs.CharDevice, opts.DevMajor, opts.DevMinor)
+		case linux.S_IFSOCK:
 			// Not yet supported.
 			return syserror.EPERM
 		default:
 			return syserror.EINVAL
 		}
+		child := fs.newDentry(childInode)
+		parent.vfsd.InsertChild(&child.vfsd, name)
+		parent.inode.impl.(*directory).childList.PushBack(child)
+		return nil
 	})
 }
 
@@ -264,7 +267,7 @@ func (fs *filesystem) OpenAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
 		if err != nil {
 			return nil, err
 		}
-		return d.open(ctx, rp, opts.Flags, false /* afterCreate */)
+		return d.open(ctx, rp, &opts, false /* afterCreate */)
 	}
 
 	mustCreate := opts.Flags&linux.O_EXCL != 0
@@ -279,7 +282,7 @@ func (fs *filesystem) OpenAt(ctx context.Context, rp *vfs.ResolvingPath, opts vf
 		if mustCreate {
 			return nil, syserror.EEXIST
 		}
-		return start.open(ctx, rp, opts.Flags, false /* afterCreate */)
+		return start.open(ctx, rp, &opts, false /* afterCreate */)
 	}
 afterTrailingSymlink:
 	parent, err := walkParentDirLocked(rp, start)
@@ -313,7 +316,7 @@ afterTrailingSymlink:
 		child := fs.newDentry(fs.newRegularFile(rp.Credentials(), opts.Mode))
 		parent.vfsd.InsertChild(&child.vfsd, name)
 		parent.inode.impl.(*directory).childList.PushBack(child)
-		return child.open(ctx, rp, opts.Flags, true)
+		return child.open(ctx, rp, &opts, true)
 	}
 	if err != nil {
 		return nil, err
@@ -327,11 +330,11 @@ afterTrailingSymlink:
 	if mustCreate {
 		return nil, syserror.EEXIST
 	}
-	return child.open(ctx, rp, opts.Flags, false)
+	return child.open(ctx, rp, &opts, false)
 }
 
-func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, flags uint32, afterCreate bool) (*vfs.FileDescription, error) {
-	ats := vfs.AccessTypesForOpenFlags(flags)
+func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, opts *vfs.OpenOptions, afterCreate bool) (*vfs.FileDescription, error) {
+	ats := vfs.AccessTypesForOpenFlags(opts.Flags)
 	if !afterCreate {
 		if err := d.inode.checkPermissions(rp.Credentials(), ats, d.inode.isDir()); err != nil {
 			return nil, err
@@ -340,10 +343,10 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, flags uint32,
 	switch impl := d.inode.impl.(type) {
 	case *regularFile:
 		var fd regularFileFD
-		if err := fd.vfsfd.Init(&fd, flags, rp.Mount(), &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
+		if err := fd.vfsfd.Init(&fd, opts.Flags, rp.Mount(), &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
 			return nil, err
 		}
-		if flags&linux.O_TRUNC != 0 {
+		if opts.Flags&linux.O_TRUNC != 0 {
 			impl.mu.Lock()
 			impl.data.Truncate(0, impl.memFile)
 			atomic.StoreUint64(&impl.size, 0)
@@ -356,7 +359,7 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, flags uint32,
 			return nil, syserror.EISDIR
 		}
 		var fd directoryFD
-		if err := fd.vfsfd.Init(&fd, flags, rp.Mount(), &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
+		if err := fd.vfsfd.Init(&fd, opts.Flags, rp.Mount(), &d.vfsd, &vfs.FileDescriptionOptions{}); err != nil {
 			return nil, err
 		}
 		return &fd.vfsfd, nil
@@ -364,7 +367,9 @@ func (d *dentry) open(ctx context.Context, rp *vfs.ResolvingPath, flags uint32,
 		// Can't open symlinks without O_PATH (which is unimplemented).
 		return nil, syserror.ELOOP
 	case *namedPipe:
-		return newNamedPipeFD(ctx, impl, rp, &d.vfsd, flags)
+		return newNamedPipeFD(ctx, impl, rp, &d.vfsd, opts.Flags)
+	case *deviceFile:
+		return rp.VirtualFilesystem().OpenDeviceSpecialFile(ctx, rp.Mount(), &d.vfsd, impl.kind, impl.major, impl.minor, opts)
 	default:
 		panic(fmt.Sprintf("unknown inode type: %T", d.inode.impl))
 	}
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 1d4889c89..515f033f2 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -149,6 +149,10 @@ type inode struct {
 	ctime int64 // nanoseconds
 	mtime int64 // nanoseconds
 
+	// Only meaningful for device special files.
+	rdevMajor uint32
+	rdevMinor uint32
+
 	impl interface{} // immutable
 }
 
@@ -269,6 +273,15 @@ func (i *inode) statTo(stat *linux.Statx) {
 		stat.Blocks = allocatedBlocksForSize(stat.Size)
 	case *namedPipe:
 		stat.Mode |= linux.S_IFIFO
+	case *deviceFile:
+		switch impl.kind {
+		case vfs.BlockDevice:
+			stat.Mode |= linux.S_IFBLK
+		case vfs.CharDevice:
+			stat.Mode |= linux.S_IFCHR
+		}
+		stat.RdevMajor = impl.major
+		stat.RdevMinor = impl.minor
 	default:
 		panic(fmt.Sprintf("unknown inode type: %T", i.impl))
 	}
@@ -309,12 +322,8 @@ func (i *inode) setStat(stat linux.Statx) error {
 			}
 		case *directory:
 			return syserror.EISDIR
-		case *symlink:
-			return syserror.EINVAL
-		case *namedPipe:
-			// Nothing.
 		default:
-			panic(fmt.Sprintf("unknown inode type: %T", i.impl))
+			return syserror.EINVAL
 		}
 	}
 	if mask&linux.STATX_ATIME != 0 {
@@ -353,13 +362,22 @@ func allocatedBlocksForSize(size uint64) uint64 {
 }
 
 func (i *inode) direntType() uint8 {
-	switch i.impl.(type) {
+	switch impl := i.impl.(type) {
 	case *regularFile:
 		return linux.DT_REG
 	case *directory:
 		return linux.DT_DIR
 	case *symlink:
 		return linux.DT_LNK
+	case *deviceFile:
+		switch impl.kind {
+		case vfs.BlockDevice:
+			return linux.DT_BLK
+		case vfs.CharDevice:
+			return linux.DT_CHR
+		default:
+			panic(fmt.Sprintf("unknown vfs.DeviceKind: %v", impl.kind))
+		}
 	default:
 		panic(fmt.Sprintf("unknown inode type: %T", i.impl))
 	}