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// Copyright 2018 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 linux
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/limits"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/usermem"
)
// rlimit describes an implementation of 'struct rlimit', which may vary from
// system-to-system.
type rlimit interface {
// toLimit converts an rlimit to a limits.Limit.
toLimit() *limits.Limit
// fromLimit converts a limits.Limit to an rlimit.
fromLimit(lim limits.Limit)
// copyIn copies an rlimit from the untrusted app to the kernel.
copyIn(t *kernel.Task, addr usermem.Addr) error
// copyOut copies an rlimit from the kernel to the untrusted app.
copyOut(t *kernel.Task, addr usermem.Addr) error
}
// newRlimit returns the appropriate rlimit type for 'struct rlimit' on this system.
func newRlimit(t *kernel.Task) (rlimit, error) {
switch t.Arch().Width() {
case 8:
// On 64-bit system, struct rlimit and struct rlimit64 are identical.
return &rlimit64{}, nil
default:
return nil, syserror.ENOSYS
}
}
type rlimit64 struct {
Cur uint64
Max uint64
}
func (r *rlimit64) toLimit() *limits.Limit {
return &limits.Limit{
Cur: limits.FromLinux(r.Cur),
Max: limits.FromLinux(r.Max),
}
}
func (r *rlimit64) fromLimit(lim limits.Limit) {
*r = rlimit64{
Cur: limits.ToLinux(lim.Cur),
Max: limits.ToLinux(lim.Max),
}
}
func (r *rlimit64) copyIn(t *kernel.Task, addr usermem.Addr) error {
_, err := t.CopyIn(addr, r)
return err
}
func (r *rlimit64) copyOut(t *kernel.Task, addr usermem.Addr) error {
_, err := t.CopyOut(addr, *r)
return err
}
func makeRlimit64(lim limits.Limit) *rlimit64 {
return &rlimit64{Cur: lim.Cur, Max: lim.Max}
}
// setableLimits is the set of supported setable limits.
var setableLimits = map[limits.LimitType]struct{}{
limits.NumberOfFiles: {},
limits.AS: {},
limits.CPU: {},
limits.Data: {},
limits.FileSize: {},
limits.MemoryLocked: {},
limits.Stack: {},
// These are not enforced, but we include them here to avoid returning
// EPERM, since some apps expect them to succeed.
limits.Core: {},
limits.ProcessCount: {},
}
func prlimit64(t *kernel.Task, resource limits.LimitType, newLim *limits.Limit) (limits.Limit, error) {
if newLim == nil {
return t.ThreadGroup().Limits().Get(resource), nil
}
if _, ok := setableLimits[resource]; !ok {
return limits.Limit{}, syserror.EPERM
}
// "A privileged process (under Linux: one with the CAP_SYS_RESOURCE
// capability in the initial user namespace) may make arbitrary changes
// to either limit value."
privileged := t.HasCapabilityIn(linux.CAP_SYS_RESOURCE, t.Kernel().RootUserNamespace())
oldLim, err := t.ThreadGroup().Limits().Set(resource, *newLim, privileged)
if err != nil {
return limits.Limit{}, err
}
if resource == limits.CPU {
t.NotifyRlimitCPUUpdated()
}
return oldLim, nil
}
// Getrlimit implements linux syscall getrlimit(2).
func Getrlimit(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
resource, ok := limits.FromLinuxResource[int(args[0].Int())]
if !ok {
// Return err; unknown limit.
return 0, nil, syserror.EINVAL
}
addr := args[1].Pointer()
rlim, err := newRlimit(t)
if err != nil {
return 0, nil, err
}
lim, err := prlimit64(t, resource, nil)
if err != nil {
return 0, nil, err
}
rlim.fromLimit(lim)
return 0, nil, rlim.copyOut(t, addr)
}
// Setrlimit implements linux syscall setrlimit(2).
func Setrlimit(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
resource, ok := limits.FromLinuxResource[int(args[0].Int())]
if !ok {
// Return err; unknown limit.
return 0, nil, syserror.EINVAL
}
addr := args[1].Pointer()
rlim, err := newRlimit(t)
if err != nil {
return 0, nil, err
}
if err := rlim.copyIn(t, addr); err != nil {
return 0, nil, syserror.EFAULT
}
_, err = prlimit64(t, resource, rlim.toLimit())
return 0, nil, err
}
// Prlimit64 implements linux syscall prlimit64(2).
func Prlimit64(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
tid := kernel.ThreadID(args[0].Int())
resource, ok := limits.FromLinuxResource[int(args[1].Int())]
if !ok {
// Return err; unknown limit.
return 0, nil, syserror.EINVAL
}
newRlimAddr := args[2].Pointer()
oldRlimAddr := args[3].Pointer()
var newLim *limits.Limit
if newRlimAddr != 0 {
var nrl rlimit64
if err := nrl.copyIn(t, newRlimAddr); err != nil {
return 0, nil, syserror.EFAULT
}
newLim = nrl.toLimit()
}
if tid < 0 {
return 0, nil, syserror.EINVAL
}
ot := t
if tid > 0 {
if ot = t.PIDNamespace().TaskWithID(tid); ot == nil {
return 0, nil, syserror.ESRCH
}
}
// "To set or get the resources of a process other than itself, the caller
// must have the CAP_SYS_RESOURCE capability, or the real, effective, and
// saved set user IDs of the target process must match the real user ID of
// the caller and the real, effective, and saved set group IDs of the
// target process must match the real group ID of the caller."
if !t.HasCapabilityIn(linux.CAP_SYS_RESOURCE, t.PIDNamespace().UserNamespace()) {
cred, tcred := t.Credentials(), ot.Credentials()
if cred.RealKUID != tcred.RealKUID ||
cred.RealKUID != tcred.EffectiveKUID ||
cred.RealKUID != tcred.SavedKUID ||
cred.RealKGID != tcred.RealKGID ||
cred.RealKGID != tcred.EffectiveKGID ||
cred.RealKGID != tcred.SavedKGID {
return 0, nil, syserror.EPERM
}
}
oldLim, err := prlimit64(ot, resource, newLim)
if err != nil {
return 0, nil, err
}
if oldRlimAddr != 0 {
if err := makeRlimit64(oldLim).copyOut(t, oldRlimAddr); err != nil {
return 0, nil, syserror.EFAULT
}
}
return 0, nil, nil
}
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