diff options
-rw-r--r-- | pkg/sentry/fsimpl/kernfs/BUILD | 1 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/kernfs/filesystem.go | 5 | ||||
-rw-r--r-- | pkg/sentry/fsimpl/kernfs/synthetic_directory.go | 102 |
3 files changed, 107 insertions, 1 deletions
diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD index 637dca70c..5e91e0536 100644 --- a/pkg/sentry/fsimpl/kernfs/BUILD +++ b/pkg/sentry/fsimpl/kernfs/BUILD @@ -83,6 +83,7 @@ go_library( "slot_list.go", "static_directory_refs.go", "symlink.go", + "synthetic_directory.go", ], visibility = ["//pkg/sentry:internal"], deps = [ diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go index c428053e8..d7d3e8f48 100644 --- a/pkg/sentry/fsimpl/kernfs/filesystem.go +++ b/pkg/sentry/fsimpl/kernfs/filesystem.go @@ -360,7 +360,10 @@ func (fs *Filesystem) MkdirAt(ctx context.Context, rp *vfs.ResolvingPath, opts v defer rp.Mount().EndWrite() childVFSD, err := parentInode.NewDir(ctx, pc, opts) if err != nil { - return err + if !opts.ForSyntheticMountpoint || err == syserror.EEXIST { + return err + } + childVFSD = newSyntheticDirectory(rp.Credentials(), opts.Mode) } parentVFSD.Impl().(*Dentry).InsertChild(pc, childVFSD.Impl().(*Dentry)) return nil diff --git a/pkg/sentry/fsimpl/kernfs/synthetic_directory.go b/pkg/sentry/fsimpl/kernfs/synthetic_directory.go new file mode 100644 index 000000000..01ba72fa8 --- /dev/null +++ b/pkg/sentry/fsimpl/kernfs/synthetic_directory.go @@ -0,0 +1,102 @@ +// Copyright 2019 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 kernfs + +import ( + "fmt" + + "gvisor.dev/gvisor/pkg/abi/linux" + "gvisor.dev/gvisor/pkg/context" + "gvisor.dev/gvisor/pkg/sentry/kernel/auth" + "gvisor.dev/gvisor/pkg/sentry/vfs" + "gvisor.dev/gvisor/pkg/syserror" +) + +// syntheticDirectory implements kernfs.Inode for a directory created by +// MkdirAt(ForSyntheticMountpoint=true). +// +// +stateify savable +type syntheticDirectory struct { + InodeAttrs + InodeNoStatFS + InodeNoopRefCount + InodeNoDynamicLookup + InodeNotSymlink + OrderedChildren + + locks vfs.FileLocks +} + +var _ Inode = (*syntheticDirectory)(nil) + +func newSyntheticDirectory(creds *auth.Credentials, perm linux.FileMode) *vfs.Dentry { + inode := &syntheticDirectory{} + inode.Init(creds, 0 /* devMajor */, 0 /* devMinor */, 0 /* ino */, perm) + d := &Dentry{} + d.Init(inode) + return &d.vfsd +} + +func (dir *syntheticDirectory) Init(creds *auth.Credentials, devMajor, devMinor uint32, ino uint64, perm linux.FileMode) { + if perm&^linux.PermissionsMask != 0 { + panic(fmt.Sprintf("perm contains non-permission bits: %#o", perm)) + } + dir.InodeAttrs.Init(creds, devMajor, devMinor, ino, linux.S_IFDIR|perm) + dir.OrderedChildren.Init(OrderedChildrenOptions{ + Writable: true, + }) +} + +// Open implements Inode.Open. +func (dir *syntheticDirectory) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) { + fd, err := NewGenericDirectoryFD(rp.Mount(), vfsd, &dir.OrderedChildren, &dir.locks, &opts, GenericDirectoryFDOptions{}) + if err != nil { + return nil, err + } + return &fd.vfsfd, nil +} + +// NewFile implements Inode.NewFile. +func (dir *syntheticDirectory) NewFile(ctx context.Context, name string, opts vfs.OpenOptions) (*vfs.Dentry, error) { + return nil, syserror.EPERM +} + +// NewDir implements Inode.NewDir. +func (dir *syntheticDirectory) NewDir(ctx context.Context, name string, opts vfs.MkdirOptions) (*vfs.Dentry, error) { + if !opts.ForSyntheticMountpoint { + return nil, syserror.EPERM + } + subdird := newSyntheticDirectory(auth.CredentialsFromContext(ctx), opts.Mode&linux.PermissionsMask) + if err := dir.OrderedChildren.Insert(name, subdird); err != nil { + subdird.DecRef(ctx) + return nil, err + } + return subdird, nil +} + +// NewLink implements Inode.NewLink. +func (dir *syntheticDirectory) NewLink(ctx context.Context, name string, target Inode) (*vfs.Dentry, error) { + return nil, syserror.EPERM +} + +// NewSymlink implements Inode.NewSymlink. +func (dir *syntheticDirectory) NewSymlink(ctx context.Context, name, target string) (*vfs.Dentry, error) { + return nil, syserror.EPERM +} + +// NewNode implements Inode.NewNode. +func (dir *syntheticDirectory) NewNode(ctx context.Context, name string, opts vfs.MknodOptions) (*vfs.Dentry, error) { + return nil, syserror.EPERM +} |