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// Copyright 2018 Google Inc.
//
// 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 linux
import (
"syscall"
"gvisor.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/bpf"
"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
)
// userSockFprog is equivalent to Linux's struct sock_fprog on amd64.
type userSockFprog struct {
// Len is the length of the filter in BPF instructions.
Len uint16
_ [6]byte // padding for alignment
// Filter is a user pointer to the struct sock_filter array that makes up
// the filter program. Filter is a uint64 rather than a usermem.Addr
// because usermem.Addr is actually uintptr, which is not a fixed-size
// type, and encoding/binary.Read objects to this.
Filter uint64
}
// Prctl implements linux syscall prctl(2).
// It has a list of subfunctions which operate on the process. The arguments are
// all based on each subfunction.
func Prctl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
option := args[0].Int()
switch option {
case linux.PR_SET_PDEATHSIG:
sig := linux.Signal(args[1].Int())
if sig != 0 && !sig.IsValid() {
return 0, nil, syscall.EINVAL
}
t.SetParentDeathSignal(sig)
return 0, nil, nil
case linux.PR_GET_PDEATHSIG:
_, err := t.CopyOut(args[1].Pointer(), int32(t.ParentDeathSignal()))
return 0, nil, err
case linux.PR_GET_KEEPCAPS:
if t.Credentials().KeepCaps {
return 1, nil, nil
}
return 0, nil, nil
case linux.PR_SET_KEEPCAPS:
val := args[1].Int()
// prctl(2): arg2 must be either 0 (permitted capabilities are cleared)
// or 1 (permitted capabilities are kept).
if val == 0 {
t.SetKeepCaps(false)
} else if val == 1 {
t.SetKeepCaps(true)
} else {
return 0, nil, syscall.EINVAL
}
return 0, nil, nil
case linux.PR_SET_NAME:
addr := args[1].Pointer()
name, err := t.CopyInString(addr, linux.TASK_COMM_LEN-1)
if err != nil && err != syscall.ENAMETOOLONG {
return 0, nil, err
}
t.SetName(name)
case linux.PR_GET_NAME:
addr := args[1].Pointer()
buf := make([]byte, linux.TASK_COMM_LEN)
len := copy(buf, t.Name())
if len < linux.TASK_COMM_LEN {
buf[len] = 0
len++
}
_, err := t.CopyOut(addr, buf[:len])
if err != nil {
return 0, nil, err
}
case linux.PR_SET_MM:
switch args[1].Int() {
case linux.PR_SET_MM_EXE_FILE:
fd := kdefs.FD(args[2].Int())
file := t.FDMap().GetFile(fd)
if file == nil {
return 0, nil, syscall.EBADF
}
defer file.DecRef()
// They trying to set exe to a non-file?
if !fs.IsFile(file.Dirent.Inode.StableAttr) {
return 0, nil, syscall.EBADF
}
// Set the underlying executable.
t.MemoryManager().SetExecutable(file.Dirent)
default:
return 0, nil, syscall.EINVAL
}
case linux.PR_SET_NO_NEW_PRIVS:
if args[1].Int() != 1 || args[2].Int() != 0 || args[3].Int() != 0 || args[4].Int() != 0 {
return 0, nil, syscall.EINVAL
}
// no_new_privs is assumed to always be set. See
// auth.Credentials.UpdateForExec.
return 0, nil, nil
case linux.PR_GET_NO_NEW_PRIVS:
if args[1].Int() != 0 || args[2].Int() != 0 || args[3].Int() != 0 || args[4].Int() != 0 {
return 0, nil, syscall.EINVAL
}
return 1, nil, nil
case linux.PR_SET_SECCOMP:
if args[1].Int() != linux.SECCOMP_MODE_FILTER {
// Unsupported mode.
return 0, nil, syscall.EINVAL
}
var fprog userSockFprog
if _, err := t.CopyIn(args[2].Pointer(), &fprog); err != nil {
return 0, nil, err
}
filter := make([]linux.BPFInstruction, int(fprog.Len))
if _, err := t.CopyIn(usermem.Addr(fprog.Filter), &filter); err != nil {
return 0, nil, err
}
compiledFilter, err := bpf.Compile(filter)
if err != nil {
t.Debugf("Invalid seccomp-bpf filter: %v", err)
return 0, nil, syscall.EINVAL
}
return 0, nil, t.AppendSyscallFilter(compiledFilter)
case linux.PR_GET_SECCOMP:
return uintptr(t.SeccompMode()), nil, nil
case linux.PR_CAPBSET_READ:
cp := linux.Capability(args[1].Uint64())
if !cp.Ok() {
return 0, nil, syscall.EINVAL
}
var rv uintptr
if auth.CapabilitySetOf(cp)&t.Credentials().BoundingCaps != 0 {
rv = 1
}
return rv, nil, nil
case linux.PR_CAPBSET_DROP:
cp := linux.Capability(args[1].Uint64())
if !cp.Ok() {
return 0, nil, syscall.EINVAL
}
return 0, nil, t.DropBoundingCapability(cp)
default:
t.Warningf("Unsupported prctl %d", option)
return 0, nil, syscall.EINVAL
}
return 0, nil, nil
}
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