github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fsimpl/kernfs/synthetic_directory.go (about)

     1  // Copyright 2019 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package kernfs
    16  
    17  import (
    18  	"fmt"
    19  
    20  	"github.com/SagerNet/gvisor/pkg/abi/linux"
    21  	"github.com/SagerNet/gvisor/pkg/context"
    22  	"github.com/SagerNet/gvisor/pkg/errors/linuxerr"
    23  	"github.com/SagerNet/gvisor/pkg/sentry/kernel/auth"
    24  	"github.com/SagerNet/gvisor/pkg/sentry/vfs"
    25  )
    26  
    27  // syntheticDirectory implements kernfs.Inode for a directory created by
    28  // MkdirAt(ForSyntheticMountpoint=true).
    29  //
    30  // +stateify savable
    31  type syntheticDirectory struct {
    32  	InodeAlwaysValid
    33  	InodeAttrs
    34  	InodeNoStatFS
    35  	InodeNotSymlink
    36  	OrderedChildren
    37  	syntheticDirectoryRefs
    38  
    39  	locks vfs.FileLocks
    40  }
    41  
    42  var _ Inode = (*syntheticDirectory)(nil)
    43  
    44  func newSyntheticDirectory(ctx context.Context, creds *auth.Credentials, perm linux.FileMode) Inode {
    45  	if perm&^linux.PermissionsMask != 0 {
    46  		panic(fmt.Sprintf("perm contains non-permission bits: %#o", perm))
    47  	}
    48  	dir := &syntheticDirectory{}
    49  	dir.InitRefs()
    50  	dir.InodeAttrs.Init(ctx, creds, 0 /* devMajor */, 0 /* devMinor */, 0 /* ino */, linux.S_IFDIR|perm)
    51  	dir.OrderedChildren.Init(OrderedChildrenOptions{
    52  		Writable: true,
    53  	})
    54  	return dir
    55  }
    56  
    57  // Open implements Inode.Open.
    58  func (dir *syntheticDirectory) Open(ctx context.Context, rp *vfs.ResolvingPath, d *Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
    59  	fd, err := NewGenericDirectoryFD(rp.Mount(), d, &dir.OrderedChildren, &dir.locks, &opts, GenericDirectoryFDOptions{})
    60  	if err != nil {
    61  		return nil, err
    62  	}
    63  	return &fd.vfsfd, nil
    64  }
    65  
    66  // NewFile implements Inode.NewFile.
    67  func (dir *syntheticDirectory) NewFile(ctx context.Context, name string, opts vfs.OpenOptions) (Inode, error) {
    68  	return nil, linuxerr.EPERM
    69  }
    70  
    71  // NewDir implements Inode.NewDir.
    72  func (dir *syntheticDirectory) NewDir(ctx context.Context, name string, opts vfs.MkdirOptions) (Inode, error) {
    73  	if !opts.ForSyntheticMountpoint {
    74  		return nil, linuxerr.EPERM
    75  	}
    76  	subdirI := newSyntheticDirectory(ctx, auth.CredentialsFromContext(ctx), opts.Mode&linux.PermissionsMask)
    77  	if err := dir.OrderedChildren.Insert(name, subdirI); err != nil {
    78  		subdirI.DecRef(ctx)
    79  		return nil, err
    80  	}
    81  	dir.TouchCMtime(ctx)
    82  	return subdirI, nil
    83  }
    84  
    85  // NewLink implements Inode.NewLink.
    86  func (dir *syntheticDirectory) NewLink(ctx context.Context, name string, target Inode) (Inode, error) {
    87  	return nil, linuxerr.EPERM
    88  }
    89  
    90  // NewSymlink implements Inode.NewSymlink.
    91  func (dir *syntheticDirectory) NewSymlink(ctx context.Context, name, target string) (Inode, error) {
    92  	return nil, linuxerr.EPERM
    93  }
    94  
    95  // NewNode implements Inode.NewNode.
    96  func (dir *syntheticDirectory) NewNode(ctx context.Context, name string, opts vfs.MknodOptions) (Inode, error) {
    97  	return nil, linuxerr.EPERM
    98  }
    99  
   100  // DecRef implements Inode.DecRef.
   101  func (dir *syntheticDirectory) DecRef(ctx context.Context) {
   102  	dir.syntheticDirectoryRefs.DecRef(func() { dir.Destroy(ctx) })
   103  }
   104  
   105  // Keep implements Inode.Keep. This is redundant because inodes will never be
   106  // created via Lookup and inodes are always valid. Makes sense to return true
   107  // because these inodes are not temporary and should only be removed on RmDir.
   108  func (dir *syntheticDirectory) Keep() bool {
   109  	return true
   110  }