132 lines
3.6 KiB
Go
132 lines
3.6 KiB
Go
// Copyright 2018 Google LLC
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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 proc
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import (
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"fmt"
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"io"
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"gvisor.googlesource.com/gvisor/pkg/sentry/context"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/fs/ramfs"
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"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
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"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
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"gvisor.googlesource.com/gvisor/pkg/syserror"
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)
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// execArgType enumerates the types of exec arguments that are exposed through
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// proc.
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type execArgType int
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const (
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cmdlineExecArg execArgType = iota
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environExecArg
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)
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// execArgFile is a file containing the exec args (either cmdline or environ)
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// for a given task.
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//
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// +stateify savable
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type execArgFile struct {
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ramfs.Entry
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// arg is the type of exec argument this file contains.
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arg execArgType
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// t is the Task to read the exec arg line from.
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t *kernel.Task
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}
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// newExecArgFile creates a file containing the exec args of the given type.
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func newExecArgFile(t *kernel.Task, msrc *fs.MountSource, arg execArgType) *fs.Inode {
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if arg != cmdlineExecArg && arg != environExecArg {
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panic(fmt.Sprintf("unknown exec arg type %v", arg))
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}
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f := &execArgFile{
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arg: arg,
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t: t,
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}
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f.InitEntry(t, fs.RootOwner, fs.FilePermsFromMode(0444))
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return newFile(f, msrc, fs.SpecialFile, t)
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}
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// DeprecatedPreadv reads the exec arg from the process's address space..
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func (f *execArgFile) DeprecatedPreadv(ctx context.Context, dst usermem.IOSequence, offset int64) (int64, error) {
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if offset < 0 {
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return 0, syserror.EINVAL
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}
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// N.B. Linux 4.2 eliminates the arbitrary one page limit.
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if offset > usermem.PageSize {
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return 0, io.EOF
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}
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dst = dst.TakeFirst64(usermem.PageSize - offset)
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m, err := getTaskMM(f.t)
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if err != nil {
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return 0, err
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}
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defer m.DecUsers(ctx)
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// Figure out the bounds of the exec arg we are trying to read.
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var execArgStart, execArgEnd usermem.Addr
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switch f.arg {
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case cmdlineExecArg:
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execArgStart, execArgEnd = m.ArgvStart(), m.ArgvEnd()
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case environExecArg:
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execArgStart, execArgEnd = m.EnvvStart(), m.EnvvEnd()
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default:
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panic(fmt.Sprintf("unknown exec arg type %v", f.arg))
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}
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if execArgStart == 0 || execArgEnd == 0 {
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// Don't attempt to read before the start/end are set up.
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return 0, io.EOF
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}
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start, ok := execArgStart.AddLength(uint64(offset))
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if !ok {
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return 0, io.EOF
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}
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if start >= execArgEnd {
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return 0, io.EOF
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}
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length := int(execArgEnd - start)
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if dstlen := dst.NumBytes(); int64(length) > dstlen {
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length = int(dstlen)
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}
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buf := make([]byte, length)
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// N.B. Technically this should be usermem.IOOpts.IgnorePermissions = true
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// until Linux 4.9 (272ddc8b3735 "proc: don't use FOLL_FORCE for reading
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// cmdline and environment").
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copyN, copyErr := m.CopyIn(ctx, start, buf, usermem.IOOpts{})
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if copyN == 0 {
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// Nothing to copy.
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return 0, copyErr
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}
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buf = buf[:copyN]
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// TODO: On Linux, if the NUL byte at the end of the
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// argument vector has been overwritten, it continues reading the
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// environment vector as part of the argument vector.
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n, dstErr := dst.CopyOut(ctx, buf)
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if dstErr != nil {
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return int64(n), dstErr
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}
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return int64(n), copyErr
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}
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