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b25f1b66ce
On supported platforms, the secrets directory is a 1MiB tmpfs. But some tasks need larger space for downloading large secrets. This is especially the case for tasks using `templates`, which need extra room to write a temporary file to the secrets directory that gets renamed to the old file atomically. This changeset allows increasing the size of the tmpfs in the `resources` block. Because this is a memory resource, we need to include it in the memory we allocate for scheduling purposes. The task is already prevented from using more memory in the tmpfs than the `resources.memory` field allows, but can bypass that limit by writing to the tmpfs via `template` or `artifact` blocks. Therefore, we need to account for the size of the tmpfs in the allocation resources. Simply adding it to the memory needed when we create the allocation allows it to be accounted for in all downstream consumers, and then we'll subtract that amount from the memory resources just before configuring the task driver. For backwards compatibility, the default value of 1MiB is "free" and ignored by the scheduler. Otherwise we'd be increasing the allocated resources for every existing alloc, which could cause problems across upgrades. If a user explicitly sets `resources.secrets = 1` it will no longer be free. Fixes: https://github.com/hashicorp/nomad/issues/2481 Ref: https://hashicorp.atlassian.net/browse/NET-10070
107 lines
2.6 KiB
Go
107 lines
2.6 KiB
Go
// Copyright (c) HashiCorp, Inc.
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// SPDX-License-Identifier: BUSL-1.1
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//go:build linux
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package allocdir
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import (
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"fmt"
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"os"
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"path/filepath"
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"syscall"
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"golang.org/x/sys/unix"
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)
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const (
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// secretMarker is the filename of the marker created so Nomad doesn't
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// try to mount the secrets tmpfs more than once
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secretMarker = ".nomad-mount"
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)
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// linkDir bind mounts src to dst as Linux doesn't support hardlinking
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// directories.
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func linkDir(src, dst string) error {
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if err := os.MkdirAll(dst, fileMode777); err != nil {
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return err
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}
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return syscall.Mount(src, dst, "", syscall.MS_BIND, "")
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}
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// mountDir bind mounts old to next using the given file mode.
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func mountDir(old, next string, uid, gid int, mode os.FileMode) error {
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if err := os.MkdirAll(next, mode); err != nil {
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return err
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}
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opts := unix.MS_BIND | unix.MS_NOSUID | unix.MS_NOATIME
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if err := unix.Mount(old, next, "", uintptr(opts), ""); err != nil {
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return err
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}
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if err := os.Chmod(next, mode); err != nil {
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return err
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}
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return os.Chown(next, uid, gid)
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}
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// unlinkDir unmounts a bind mounted directory as Linux doesn't support
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// hardlinking directories. If the dir is already unmounted no error is
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// returned.
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func unlinkDir(dir string) error {
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if err := syscall.Unmount(dir, 0); err != nil {
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if err != syscall.EINVAL {
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return err
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}
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}
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return nil
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}
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// createSecretDir creates the secrets dir folder at the given path using a
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// tmpfs
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func createSecretDir(dir string, size int) error {
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// Only mount the tmpfs if we are root
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if unix.Geteuid() == 0 {
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if err := os.MkdirAll(dir, fileMode777); err != nil {
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return err
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}
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// Check for marker file and skip mounting if it exists
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marker := filepath.Join(dir, secretMarker)
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if _, err := os.Stat(marker); err == nil {
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return nil
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}
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flags := uintptr(syscall.MS_NOEXEC)
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options := fmt.Sprintf("size=%dm", size)
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if err := syscall.Mount("tmpfs", dir, "tmpfs", flags, options); err != nil {
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return os.NewSyscallError("mount", err)
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}
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// Create the marker file so we don't try to mount more than once
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f, err := os.OpenFile(marker, os.O_RDWR|os.O_CREATE, fileMode666)
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if err != nil {
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// Hard fail since if this fails something is really wrong
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return err
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}
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f.Close()
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return nil
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}
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return os.MkdirAll(dir, fileMode777)
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}
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// createSecretDir removes the secrets dir folder
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func removeSecretDir(dir string) error {
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if unix.Geteuid() == 0 {
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if err := unlinkDir(dir); err != nil {
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// Ignore invalid path errors
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if err != syscall.ENOENT {
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return os.NewSyscallError("unmount", err)
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}
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}
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}
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return os.RemoveAll(dir)
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}
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