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Shailend ChandandgVisor bot
b943164ed6
A tty inode was kept alive by a single ownership chain: the stdio file description's reference on the import-time dentry. Everything else that used the inode referred to it uncounted: a file description opened via /dev/tty pins only the devtmpfs dentry, and the controlling-terminal association (ThreadGroup.tty) is a bare pointer. PiperOrigin-RevId: 962479941
90 lines
2.7 KiB
Go
90 lines
2.7 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package devpts
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import (
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/context"
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"gvisor.dev/gvisor/pkg/errors/linuxerr"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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)
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// Terminal is a pseudoterminal.
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//
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// Terminal implements kernel.TTYOperations.
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//
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// +stateify savable
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type Terminal struct {
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// n is the terminal index. It is immutable.
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n uint32
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// ld is the line discipline of the terminal. It is immutable.
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ld *lineDiscipline
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// root is the rootInode for this devpts mount. It is immutable.
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root *rootInode
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// masterKTTY contains the controlling process of the master end of
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// this terminal. This field is immutable.
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masterKTTY *kernel.TTY
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// replicaKTTY contains the controlling process of the replica end of this
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// terminal. This field is immutable.
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replicaKTTY *kernel.TTY
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}
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var _ kernel.TTYOperations = (*Terminal)(nil)
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// IncRef implements kernel.TTYOperations.IncRef.
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//
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// A devpts Terminal is kept alive by its master file description and the
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// rootInode.replicas map rather than by a reference count.
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func (t *Terminal) IncRef() {}
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// DecRef implements kernel.TTYOperations.DecRef.
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func (t *Terminal) DecRef(context.Context) {}
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// OpenTTY implements kernel.TTYOperations.OpenTTY.
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func (t *Terminal) OpenTTY(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
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tsk := kernel.TaskFromContext(ctx)
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if tsk == nil {
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return nil, linuxerr.EIO
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}
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t.root.mu.Lock()
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ri, ok := t.root.replicas[t.replicaKTTY.Index()]
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t.root.mu.Unlock()
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if !ok {
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return nil, linuxerr.EIO
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}
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fd := &replicaFileDescription{
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inode: ri,
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}
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fd.LockFD.Init(&ri.locks)
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if err := fd.vfsfd.Init(fd, opts.Flags, tsk.Credentials(), mnt, vfsd, &vfs.FileDescriptionOptions{
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SpecialFile: true,
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}); err != nil {
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return nil, err
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}
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if opts.Flags&linux.O_NOCTTY == 0 {
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// Opening a replica sets the process' controlling TTY when
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// possible. An error indicates it cannot be set, and is
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// ignored silently. See Linux tty_open().
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_ = tsk.ThreadGroup().SetControllingTTY(ctx, t.replicaKTTY, false /* steal */, fd.vfsfd.IsReadable())
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}
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ri.t.ld.replicaOpen()
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return &fd.vfsfd, nil
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}
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