diff options
Diffstat (limited to 'pkg/sentry/fsimpl/host/host.go')
| -rw-r--r-- | pkg/sentry/fsimpl/host/host.go | 258 |
1 files changed, 239 insertions, 19 deletions
diff --git a/pkg/sentry/fsimpl/host/host.go b/pkg/sentry/fsimpl/host/host.go index 2eebcd60c..3afb41395 100644 --- a/pkg/sentry/fsimpl/host/host.go +++ b/pkg/sentry/fsimpl/host/host.go @@ -19,18 +19,23 @@ package host import ( "errors" "fmt" + "math" "syscall" "golang.org/x/sys/unix" "gvisor.dev/gvisor/pkg/abi/linux" "gvisor.dev/gvisor/pkg/context" + "gvisor.dev/gvisor/pkg/fd" "gvisor.dev/gvisor/pkg/log" "gvisor.dev/gvisor/pkg/refs" + "gvisor.dev/gvisor/pkg/safemem" "gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs" "gvisor.dev/gvisor/pkg/sentry/kernel/auth" + "gvisor.dev/gvisor/pkg/sentry/memmap" "gvisor.dev/gvisor/pkg/sentry/vfs" "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/syserror" + "gvisor.dev/gvisor/pkg/usermem" ) // filesystem implements vfs.FilesystemImpl. @@ -70,10 +75,20 @@ func ImportFD(mnt *vfs.Mount, hostFD int, ownerUID auth.KUID, ownerGID auth.KGID hostFD: hostFD, isStream: isStream, isTTY: isTTY, + canMap: canMap(uint32(fileType)), ino: fs.NextIno(), mode: fileMode, uid: ownerUID, gid: ownerGID, + // For simplicity, set offset to 0. Technically, we should + // only set to 0 on files that are not seekable (sockets, pipes, etc.), + // and use the offset from the host fd otherwise. + offset: 0, + } + + // These files can't be memory mapped, assert this. + if i.isStream && i.canMap { + panic("files that can return EWOULDBLOCK (sockets, pipes, etc.) cannot be memory mapped") } d := &kernfs.Dentry{} @@ -110,12 +125,17 @@ type inode struct { // This field is initialized at creation time and is immutable. isTTY bool + // canMap specifies whether we allow the file to be memory mapped. + // + // This field is initialized at creation time and is immutable. + canMap bool + // ino is an inode number unique within this filesystem. + // + // This field is initialized at creation time and is immutable. ino uint64 - // mu protects the inode metadata below. - // TODO(gvisor.dev/issue/1672): actually protect fields below. - //mu sync.Mutex + // TODO(gvisor.dev/issue/1672): protect mode, uid, and gid with mutex. // mode is the file mode of this inode. Note that this value may become out // of date if the mode is changed on the host, e.g. with chmod. @@ -125,6 +145,12 @@ type inode struct { // file created on import, not the fd on the host. uid auth.KUID gid auth.KGID + + // offsetMu protects offset. + offsetMu sync.Mutex + + // offset specifies the current file offset. + offset int64 } // Note that these flags may become out of date, since they can be modified @@ -336,36 +362,40 @@ func (i *inode) open(d *vfs.Dentry, mnt *vfs.Mount) (*vfs.FileDescription, error // TODO(gvisor.dev/issue/1672): Whitelist specific file types here, so that // we don't allow importing arbitrary file types without proper support. + var ( + vfsfd *vfs.FileDescription + fdImpl vfs.FileDescriptionImpl + ) if i.isTTY { - // TODO(gvisor.dev/issue/1672): support importing host fd as TTY. - return nil, errors.New("importing host fd as TTY not supported") - } - - // For simplicity, set offset to 0. Technically, we should - // only set to 0 on files that are not seekable (sockets, pipes, etc.), - // and use the offset from the host fd otherwise. - fd := &defaultFileFD{ - fileDescription: fileDescription{ - inode: i, - }, - canMap: canMap(uint32(fileType)), - mu: sync.Mutex{}, - offset: 0, + fd := &ttyFD{ + fileDescription: fileDescription{inode: i}, + termios: linux.DefaultSlaveTermios, + } + vfsfd = &fd.vfsfd + fdImpl = fd + } else { + // For simplicity, set offset to 0. Technically, we should + // only set to 0 on files that are not seekable (sockets, pipes, etc.), + // and use the offset from the host fd otherwise. + fd := &fileDescription{inode: i} + vfsfd = &fd.vfsfd + fdImpl = fd } - vfsfd := &fd.vfsfd flags, err := fileFlagsFromHostFD(i.hostFD) if err != nil { return nil, err } - if err := vfsfd.Init(fd, uint32(flags), mnt, d, &vfs.FileDescriptionOptions{}); err != nil { + if err := vfsfd.Init(fdImpl, uint32(flags), mnt, d, &vfs.FileDescriptionOptions{}); err != nil { return nil, err } return vfsfd, nil } // fileDescription is embedded by host fd implementations of FileDescriptionImpl. +// +// TODO(gvisor.dev/issue/1672): Implement Waitable interface. type fileDescription struct { vfsfd vfs.FileDescription vfs.FileDescriptionDefaultImpl @@ -394,3 +424,193 @@ func (f *fileDescription) Stat(_ context.Context, opts vfs.StatOptions) (linux.S func (f *fileDescription) Release() { // noop } + +// PRead implements FileDescriptionImpl. +func (f *fileDescription) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) { + i := f.inode + // TODO(b/34716638): Some char devices do support offsets, e.g. /dev/null. + if i.isStream { + return 0, syserror.ESPIPE + } + + return readFromHostFD(ctx, i.hostFD, dst, offset, opts.Flags) +} + +// Read implements FileDescriptionImpl. +func (f *fileDescription) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) { + i := f.inode + // TODO(b/34716638): Some char devices do support offsets, e.g. /dev/null. + if i.isStream { + n, err := readFromHostFD(ctx, i.hostFD, dst, -1, opts.Flags) + if isBlockError(err) { + // If we got any data at all, return it as a "completed" partial read + // rather than retrying until complete. + if n != 0 { + err = nil + } else { + err = syserror.ErrWouldBlock + } + } + return n, err + } + // TODO(gvisor.dev/issue/1672): Cache pages, when forced to do so. + i.offsetMu.Lock() + n, err := readFromHostFD(ctx, i.hostFD, dst, i.offset, opts.Flags) + i.offset += n + i.offsetMu.Unlock() + return n, err +} + +func readFromHostFD(ctx context.Context, hostFD int, dst usermem.IOSequence, offset int64, flags uint32) (int64, error) { + // TODO(gvisor.dev/issue/1672): Support select preadv2 flags. + if flags != 0 { + return 0, syserror.EOPNOTSUPP + } + + var reader safemem.Reader + if offset == -1 { + reader = safemem.FromIOReader{fd.NewReadWriter(hostFD)} + } else { + reader = safemem.FromVecReaderFunc{ + func(srcs [][]byte) (int64, error) { + n, err := unix.Preadv(hostFD, srcs, offset) + return int64(n), err + }, + } + } + n, err := dst.CopyOutFrom(ctx, reader) + return int64(n), err +} + +// PWrite implements FileDescriptionImpl. +func (f *fileDescription) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) { + i := f.inode + // TODO(b/34716638): Some char devices do support offsets, e.g. /dev/null. + if i.isStream { + return 0, syserror.ESPIPE + } + + return writeToHostFD(ctx, i.hostFD, src, offset, opts.Flags) +} + +// Write implements FileDescriptionImpl. +func (f *fileDescription) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) { + i := f.inode + // TODO(b/34716638): Some char devices do support offsets, e.g. /dev/null. + if i.isStream { + n, err := writeToHostFD(ctx, i.hostFD, src, -1, opts.Flags) + if isBlockError(err) { + err = syserror.ErrWouldBlock + } + return n, err + } + // TODO(gvisor.dev/issue/1672): Cache pages, when forced to do so. + // TODO(gvisor.dev/issue/1672): Write to end of file and update offset if O_APPEND is set on this file. + i.offsetMu.Lock() + n, err := writeToHostFD(ctx, i.hostFD, src, i.offset, opts.Flags) + i.offset += n + i.offsetMu.Unlock() + return n, err +} + +func writeToHostFD(ctx context.Context, hostFD int, src usermem.IOSequence, offset int64, flags uint32) (int64, error) { + // TODO(gvisor.dev/issue/1672): Support select pwritev2 flags. + if flags != 0 { + return 0, syserror.EOPNOTSUPP + } + + var writer safemem.Writer + if offset == -1 { + writer = safemem.FromIOWriter{fd.NewReadWriter(hostFD)} + } else { + writer = safemem.FromVecWriterFunc{ + func(srcs [][]byte) (int64, error) { + n, err := unix.Pwritev(hostFD, srcs, offset) + return int64(n), err + }, + } + } + n, err := src.CopyInTo(ctx, writer) + return int64(n), err +} + +// Seek implements FileDescriptionImpl. +// +// Note that we do not support seeking on directories, since we do not even +// allow directory fds to be imported at all. +func (f *fileDescription) Seek(_ context.Context, offset int64, whence int32) (int64, error) { + i := f.inode + // TODO(b/34716638): Some char devices do support seeking, e.g. /dev/null. + if i.isStream { + return 0, syserror.ESPIPE + } + + i.offsetMu.Lock() + defer i.offsetMu.Unlock() + + switch whence { + case linux.SEEK_SET: + if offset < 0 { + return i.offset, syserror.EINVAL + } + i.offset = offset + + case linux.SEEK_CUR: + // Check for overflow. Note that underflow cannot occur, since i.offset >= 0. + if offset > math.MaxInt64-i.offset { + return i.offset, syserror.EOVERFLOW + } + if i.offset+offset < 0 { + return i.offset, syserror.EINVAL + } + i.offset += offset + + case linux.SEEK_END: + var s syscall.Stat_t + if err := syscall.Fstat(i.hostFD, &s); err != nil { + return i.offset, err + } + size := s.Size + + // Check for overflow. Note that underflow cannot occur, since size >= 0. + if offset > math.MaxInt64-size { + return i.offset, syserror.EOVERFLOW + } + if size+offset < 0 { + return i.offset, syserror.EINVAL + } + i.offset = size + offset + + case linux.SEEK_DATA, linux.SEEK_HOLE: + // Modifying the offset in the host file table should not matter, since + // this is the only place where we use it. + // + // For reading and writing, we always rely on our internal offset. + n, err := unix.Seek(i.hostFD, offset, int(whence)) + if err != nil { + return i.offset, err + } + i.offset = n + + default: + // Invalid whence. + return i.offset, syserror.EINVAL + } + + return i.offset, nil +} + +// Sync implements FileDescriptionImpl. +func (f *fileDescription) Sync(context.Context) error { + // TODO(gvisor.dev/issue/1672): Currently we do not support the SyncData optimization, so we always sync everything. + return unix.Fsync(f.inode.hostFD) +} + +// ConfigureMMap implements FileDescriptionImpl. +func (f *fileDescription) ConfigureMMap(_ context.Context, opts *memmap.MMapOpts) error { + if !f.inode.canMap { + return syserror.ENODEV + } + // TODO(gvisor.dev/issue/1672): Implement ConfigureMMap and Mappable interface. + return syserror.ENODEV +} |