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/*
* cache.go - Handles cache clearing and management.
*
* Copyright 2017 Google Inc.
* Author: Joe Richey (joerichey@google.com)
*
* 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 security
import (
"log"
"os"
"golang.org/x/sys/unix"
)
// DropFilesystemCache instructs the kernel to free the reclaimable inodes and
// dentries. This has the effect of making encrypted directories whose keys are
// not present no longer accessible. Requires root privileges.
func DropFilesystemCache() error {
// Dirty reclaimable inodes must be synced so that they will be freed.
log.Print("syncing changes to filesystem")
unix.Sync()
// See: https://www.kernel.org/doc/Documentation/sysctl/vm.txt
log.Print("freeing reclaimable inodes and dentries")
file, err := os.OpenFile("/proc/sys/vm/drop_caches", os.O_WRONLY|os.O_SYNC, 0)
if err != nil {
return err
}
defer file.Close()
// "2" just frees the reclaimable inodes and dentries. The associated
// pages to these inodes will be freed. We do not need to free the
// entire pagecache (as this will severely impact performance).
_, err = file.WriteString("2")
return err
}
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