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// Copyright 2021 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 cmd
import (
"context"
"fmt"
"io/ioutil"
"github.com/google/subcommands"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/runsc/flag"
"gvisor.dev/gvisor/runsc/mitigate"
)
const (
// cpuInfo is the path used to parse CPU info.
cpuInfo = "/proc/cpuinfo"
// allPossibleCPUs is the path used to enable CPUs.
allPossibleCPUs = "/sys/devices/system/cpu/possible"
)
// Mitigate implements subcommands.Command for the "mitigate" command.
type Mitigate struct {
// Run the command without changing the underlying system.
dryRun bool
// Reverse mitigate by turning on all CPU cores.
reverse bool
// Path to file to read to create CPUSet.
path string
// Callback to check if a given thread is vulnerable.
vulnerable func(other mitigate.Thread) bool
}
// Name implements subcommands.command.name.
func (*Mitigate) Name() string {
return "mitigate"
}
// Synopsis implements subcommands.Command.Synopsis.
func (*Mitigate) Synopsis() string {
return "mitigate mitigates the underlying system against side channel attacks"
}
// Usage implments Usage for cmd.Mitigate.
func (m Mitigate) Usage() string {
return `mitigate [flags]
mitigate mitigates a system to the "MDS" vulnerability by implementing a manual shutdown of SMT. The command checks /proc/cpuinfo for cpus having the MDS vulnerability, and if found, shutdown all but one CPU per hyperthread pair via /sys/devices/system/cpu/cpu{N}/online. CPUs can be restored by writing "2" to each file in /sys/devices/system/cpu/cpu{N}/online or performing a system reboot.
The command can be reversed with --reverse, which reads the total CPUs from /sys/devices/system/cpu/possible and enables all with /sys/devices/system/cpu/cpu{N}/online.`
}
// SetFlags sets flags for the command Mitigate.
func (m *Mitigate) SetFlags(f *flag.FlagSet) {
f.BoolVar(&m.dryRun, "dryrun", false, "run the command without changing system")
f.BoolVar(&m.reverse, "reverse", false, "reverse mitigate by enabling all CPUs")
}
// Execute implements subcommands.Command.Execute.
func (m *Mitigate) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
if f.NArg() != 0 {
f.Usage()
return subcommands.ExitUsageError
}
m.path = cpuInfo
if m.reverse {
m.path = allPossibleCPUs
}
m.vulnerable = func(other mitigate.Thread) bool {
return other.IsVulnerable()
}
if _, err := m.doExecute(); err != nil {
log.Warningf("Execute failed: %v", err)
return subcommands.ExitFailure
}
return subcommands.ExitSuccess
}
// Execute executes the Mitigate command.
func (m *Mitigate) doExecute() (mitigate.CPUSet, error) {
if m.dryRun {
log.Infof("Running with DryRun. No cpu settings will be changed.")
}
if m.reverse {
data, err := ioutil.ReadFile(m.path)
if err != nil {
return nil, fmt.Errorf("failed to read %s: %v", m.path, err)
}
set, err := m.doReverse(data)
if err != nil {
return nil, fmt.Errorf("reverse operation failed: %v", err)
}
return set, nil
}
data, err := ioutil.ReadFile(m.path)
if err != nil {
return nil, fmt.Errorf("failed to read %s: %v", m.path, err)
}
set, err := m.doMitigate(data)
if err != nil {
return nil, fmt.Errorf("mitigate operation failed: %v", err)
}
return set, nil
}
func (m *Mitigate) doMitigate(data []byte) (mitigate.CPUSet, error) {
set, err := mitigate.NewCPUSet(data, m.vulnerable)
if err != nil {
return nil, err
}
log.Infof("Mitigate found the following CPUs...")
log.Infof("%s", set)
disableList := set.GetShutdownList()
log.Infof("Disabling threads on thread pairs.")
for _, t := range disableList {
log.Infof("Disable thread: %s", t)
if m.dryRun {
continue
}
if err := t.Disable(); err != nil {
return nil, fmt.Errorf("error disabling thread: %s err: %v", t, err)
}
}
log.Infof("Shutdown successful.")
return set, nil
}
func (m *Mitigate) doReverse(data []byte) (mitigate.CPUSet, error) {
set, err := mitigate.NewCPUSetFromPossible(data)
if err != nil {
return nil, err
}
log.Infof("Reverse mitigate found the following CPUs...")
log.Infof("%s", set)
enableList := set.GetRemainingList()
log.Infof("Enabling all CPUs...")
for _, t := range enableList {
log.Infof("Enabling thread: %s", t)
if m.dryRun {
continue
}
if err := t.Enable(); err != nil {
return nil, fmt.Errorf("error enabling thread: %s err: %v", t, err)
}
}
log.Infof("Enable successful.")
return set, nil
}
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