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mount.go
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mount.go
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package mounts
import (
"context"
"fmt"
"os"
"path/filepath"
"sync"
"time"
"github.com/moby/buildkit/util/bklog"
"github.com/containerd/containerd/mount"
"github.com/containerd/containerd/pkg/userns"
"github.com/docker/docker/pkg/idtools"
"github.com/moby/buildkit/cache"
"github.com/moby/buildkit/client"
"github.com/moby/buildkit/identity"
"github.com/moby/buildkit/session"
"github.com/moby/buildkit/session/secrets"
"github.com/moby/buildkit/session/sshforward"
"github.com/moby/buildkit/snapshot"
"github.com/moby/buildkit/solver/pb"
"github.com/moby/buildkit/util/grpcerrors"
"github.com/moby/locker"
"github.com/pkg/errors"
"google.golang.org/grpc/codes"
)
func NewMountManager(name string, cm cache.Manager, sm *session.Manager) *MountManager {
return &MountManager{
cm: cm,
sm: sm,
cacheMounts: map[string]*cacheRefShare{},
managerName: name,
}
}
type MountManager struct {
cm cache.Manager
sm *session.Manager
cacheMountsMu sync.Mutex
cacheMounts map[string]*cacheRefShare
managerName string
}
func (mm *MountManager) getRefCacheDir(ctx context.Context, ref cache.ImmutableRef, id string, m *pb.Mount, sharing pb.CacheSharingOpt, s session.Group) (mref cache.MutableRef, err error) {
g := &cacheRefGetter{
locker: &mm.cacheMountsMu,
cacheMounts: mm.cacheMounts,
cm: mm.cm,
globalCacheRefs: sharedCacheRefs,
name: fmt.Sprintf("cached mount %s from %s", m.Dest, mm.managerName),
session: s,
}
return g.getRefCacheDir(ctx, ref, id, sharing)
}
type cacheRefGetter struct {
locker sync.Locker
cacheMounts map[string]*cacheRefShare
cm cache.Manager
globalCacheRefs *cacheRefs
name string
session session.Group
}
func (g *cacheRefGetter) getRefCacheDir(ctx context.Context, ref cache.ImmutableRef, id string, sharing pb.CacheSharingOpt) (mref cache.MutableRef, err error) {
key := id
if ref != nil {
key += ":" + ref.ID()
}
mu := g.locker
mu.Lock()
defer mu.Unlock()
if ref, ok := g.cacheMounts[key]; ok {
return ref.clone(), nil
}
defer func() {
if err == nil {
share := &cacheRefShare{MutableRef: mref, refs: map[*cacheRef]struct{}{}}
g.cacheMounts[key] = share
mref = share.clone()
}
}()
switch sharing {
case pb.CacheSharingOpt_SHARED:
return g.globalCacheRefs.get(key, func() (cache.MutableRef, error) {
return g.getRefCacheDirNoCache(ctx, key, ref, id, false)
})
case pb.CacheSharingOpt_PRIVATE:
return g.getRefCacheDirNoCache(ctx, key, ref, id, false)
case pb.CacheSharingOpt_LOCKED:
return g.getRefCacheDirNoCache(ctx, key, ref, id, true)
default:
return nil, errors.Errorf("invalid cache sharing option: %s", sharing.String())
}
}
func (g *cacheRefGetter) getRefCacheDirNoCache(ctx context.Context, key string, ref cache.ImmutableRef, id string, block bool) (cache.MutableRef, error) {
makeMutable := func(ref cache.ImmutableRef) (cache.MutableRef, error) {
return g.cm.New(ctx, ref, g.session, cache.WithRecordType(client.UsageRecordTypeCacheMount), cache.WithDescription(g.name), cache.CachePolicyRetain)
}
cacheRefsLocker.Lock(key)
defer cacheRefsLocker.Unlock(key)
for {
sis, err := SearchCacheDir(ctx, g.cm, key)
if err != nil {
return nil, err
}
locked := false
for _, si := range sis {
if mRef, err := g.cm.GetMutable(ctx, si.ID()); err == nil {
bklog.G(ctx).Debugf("reusing ref for cache dir: %s", mRef.ID())
return mRef, nil
} else if errors.Is(err, cache.ErrLocked) {
locked = true
}
}
if block && locked {
cacheRefsLocker.Unlock(key)
select {
case <-ctx.Done():
cacheRefsLocker.Lock(key)
return nil, ctx.Err()
case <-time.After(100 * time.Millisecond):
cacheRefsLocker.Lock(key)
}
} else {
break
}
}
mRef, err := makeMutable(ref)
if err != nil {
return nil, err
}
md := CacheRefMetadata{mRef}
if err := md.setCacheDirIndex(key); err != nil {
mRef.Release(context.TODO())
return nil, err
}
return mRef, nil
}
func (mm *MountManager) getSSHMountable(ctx context.Context, m *pb.Mount, g session.Group) (cache.Mountable, error) {
var caller session.Caller
err := mm.sm.Any(ctx, g, func(ctx context.Context, _ string, c session.Caller) error {
if err := sshforward.CheckSSHID(ctx, c, m.SSHOpt.ID); err != nil {
if m.SSHOpt.Optional {
return nil
}
if grpcerrors.Code(err) == codes.Unimplemented {
return errors.Errorf("no SSH key %q forwarded from the client", m.SSHOpt.ID)
}
return err
}
caller = c
return nil
})
if err != nil {
return nil, err
}
if caller == nil {
return nil, nil
}
// because ssh socket remains active, to actually handle session disconnecting ssh error
// should restart the whole exec with new session
return &sshMount{mount: m, caller: caller, idmap: mm.cm.IdentityMapping()}, nil
}
type sshMount struct {
mount *pb.Mount
caller session.Caller
idmap *idtools.IdentityMapping
}
func (sm *sshMount) Mount(ctx context.Context, readonly bool, g session.Group) (snapshot.Mountable, error) {
return &sshMountInstance{sm: sm, idmap: sm.idmap}, nil
}
type sshMountInstance struct {
sm *sshMount
idmap *idtools.IdentityMapping
}
func (sm *sshMountInstance) Mount() ([]mount.Mount, func() error, error) {
ctx, cancel := context.WithCancel(context.TODO())
uid := int(sm.sm.mount.SSHOpt.Uid)
gid := int(sm.sm.mount.SSHOpt.Gid)
if sm.idmap != nil {
identity, err := sm.idmap.ToHost(idtools.Identity{
UID: uid,
GID: gid,
})
if err != nil {
cancel()
return nil, nil, err
}
uid = identity.UID
gid = identity.GID
}
sock, cleanup, err := sshforward.MountSSHSocket(ctx, sm.sm.caller, sshforward.SocketOpt{
ID: sm.sm.mount.SSHOpt.ID,
UID: uid,
GID: gid,
Mode: int(sm.sm.mount.SSHOpt.Mode & 0777),
})
if err != nil {
cancel()
return nil, nil, err
}
release := func() error {
var err error
if cleanup != nil {
err = cleanup()
}
cancel()
return err
}
return []mount.Mount{{
Type: "bind",
Source: sock,
Options: []string{"rbind"},
}}, release, nil
}
func (sm *sshMountInstance) IdentityMapping() *idtools.IdentityMapping {
return sm.idmap
}
func (mm *MountManager) getSecretMountable(ctx context.Context, m *pb.Mount, g session.Group) (cache.Mountable, error) {
if m.SecretOpt == nil {
return nil, errors.Errorf("invalid secret mount options")
}
sopt := *m.SecretOpt
id := sopt.ID
if id == "" {
return nil, errors.Errorf("secret ID missing from mount options")
}
var dt []byte
var err error
err = mm.sm.Any(ctx, g, func(ctx context.Context, _ string, caller session.Caller) error {
dt, err = secrets.GetSecret(ctx, caller, id)
if err != nil {
if errors.Is(err, secrets.ErrNotFound) && m.SecretOpt.Optional {
return nil
}
return err
}
return nil
})
if err != nil {
return nil, err
}
return &secretMount{mount: m, data: dt, idmap: mm.cm.IdentityMapping()}, nil
}
type secretMount struct {
mount *pb.Mount
data []byte
idmap *idtools.IdentityMapping
}
func (sm *secretMount) Mount(ctx context.Context, readonly bool, g session.Group) (snapshot.Mountable, error) {
return &secretMountInstance{sm: sm, idmap: sm.idmap}, nil
}
type secretMountInstance struct {
sm *secretMount
root string
idmap *idtools.IdentityMapping
}
func (sm *secretMountInstance) Mount() ([]mount.Mount, func() error, error) {
dir, err := os.MkdirTemp("", "buildkit-secrets")
if err != nil {
return nil, nil, errors.Wrap(err, "failed to create temp dir")
}
cleanupDir := func() error {
return os.RemoveAll(dir)
}
if err := os.Chmod(dir, 0711); err != nil {
cleanupDir()
return nil, nil, err
}
tmpMount := mount.Mount{
Type: "tmpfs",
Source: "tmpfs",
Options: []string{"nodev", "nosuid", "noexec", fmt.Sprintf("uid=%d,gid=%d", os.Geteuid(), os.Getegid())},
}
if userns.RunningInUserNS() {
tmpMount.Options = nil
}
if err := mount.All([]mount.Mount{tmpMount}, dir); err != nil {
cleanupDir()
return nil, nil, errors.Wrap(err, "unable to setup secret mount")
}
sm.root = dir
cleanup := func() error {
if err := mount.Unmount(dir, 0); err != nil {
return err
}
return cleanupDir()
}
randID := identity.NewID()
fp := filepath.Join(dir, randID)
if err := os.WriteFile(fp, sm.sm.data, 0600); err != nil {
cleanup()
return nil, nil, err
}
uid := int(sm.sm.mount.SecretOpt.Uid)
gid := int(sm.sm.mount.SecretOpt.Gid)
if sm.idmap != nil {
identity, err := sm.idmap.ToHost(idtools.Identity{
UID: uid,
GID: gid,
})
if err != nil {
cleanup()
return nil, nil, err
}
uid = identity.UID
gid = identity.GID
}
if err := os.Chown(fp, uid, gid); err != nil {
cleanup()
return nil, nil, err
}
if err := os.Chmod(fp, os.FileMode(sm.sm.mount.SecretOpt.Mode&0777)); err != nil {
cleanup()
return nil, nil, err
}
return []mount.Mount{{
Type: "bind",
Source: fp,
Options: []string{"ro", "rbind", "nodev", "nosuid", "noexec"},
}}, cleanup, nil
}
func (sm *secretMountInstance) IdentityMapping() *idtools.IdentityMapping {
return sm.idmap
}
func (mm *MountManager) MountableCache(ctx context.Context, m *pb.Mount, ref cache.ImmutableRef, g session.Group) (cache.MutableRef, error) {
if m.CacheOpt == nil {
return nil, errors.Errorf("missing cache mount options")
}
return mm.getRefCacheDir(ctx, ref, m.CacheOpt.ID, m, m.CacheOpt.Sharing, g)
}
func (mm *MountManager) MountableTmpFS(m *pb.Mount) cache.Mountable {
return newTmpfs(mm.cm.IdentityMapping(), m.TmpfsOpt)
}
func (mm *MountManager) MountableSecret(ctx context.Context, m *pb.Mount, g session.Group) (cache.Mountable, error) {
return mm.getSecretMountable(ctx, m, g)
}
func (mm *MountManager) MountableSSH(ctx context.Context, m *pb.Mount, g session.Group) (cache.Mountable, error) {
return mm.getSSHMountable(ctx, m, g)
}
func newTmpfs(idmap *idtools.IdentityMapping, opt *pb.TmpfsOpt) cache.Mountable {
return &tmpfs{idmap: idmap, opt: opt}
}
type tmpfs struct {
idmap *idtools.IdentityMapping
opt *pb.TmpfsOpt
}
func (f *tmpfs) Mount(ctx context.Context, readonly bool, g session.Group) (snapshot.Mountable, error) {
return &tmpfsMount{readonly: readonly, idmap: f.idmap, opt: f.opt}, nil
}
type tmpfsMount struct {
readonly bool
idmap *idtools.IdentityMapping
opt *pb.TmpfsOpt
}
func (m *tmpfsMount) Mount() ([]mount.Mount, func() error, error) {
opt := []string{"nosuid"}
if m.readonly {
opt = append(opt, "ro")
}
if m.opt != nil {
if m.opt.Size_ > 0 {
opt = append(opt, fmt.Sprintf("size=%d", m.opt.Size_))
}
}
return []mount.Mount{{
Type: "tmpfs",
Source: "tmpfs",
Options: opt,
}}, func() error { return nil }, nil
}
func (m *tmpfsMount) IdentityMapping() *idtools.IdentityMapping {
return m.idmap
}
var cacheRefsLocker = locker.New()
var sharedCacheRefs = &cacheRefs{}
type cacheRefs struct {
mu sync.Mutex
shares map[string]*cacheRefShare
}
// ClearActiveCacheMounts clears shared cache mounts currently in use.
// Caller needs to hold CacheMountsLocker before calling
func ClearActiveCacheMounts() {
sharedCacheRefs.shares = nil
}
func CacheMountsLocker() sync.Locker {
return &sharedCacheRefs.mu
}
func (r *cacheRefs) get(key string, fn func() (cache.MutableRef, error)) (cache.MutableRef, error) {
r.mu.Lock()
defer r.mu.Unlock()
if r.shares == nil {
r.shares = map[string]*cacheRefShare{}
}
share, ok := r.shares[key]
if ok {
return share.clone(), nil
}
mref, err := fn()
if err != nil {
return nil, err
}
share = &cacheRefShare{MutableRef: mref, main: r, key: key, refs: map[*cacheRef]struct{}{}}
r.shares[key] = share
return share.clone(), nil
}
type cacheRefShare struct {
cache.MutableRef
mu sync.Mutex
refs map[*cacheRef]struct{}
main *cacheRefs
key string
}
func (r *cacheRefShare) clone() cache.MutableRef {
cacheRef := &cacheRef{cacheRefShare: r}
if cacheRefCloneHijack != nil {
cacheRefCloneHijack()
}
r.mu.Lock()
r.refs[cacheRef] = struct{}{}
r.mu.Unlock()
return cacheRef
}
func (r *cacheRefShare) release(ctx context.Context) error {
if r.main != nil {
delete(r.main.shares, r.key)
}
return r.MutableRef.Release(ctx)
}
var cacheRefReleaseHijack func()
var cacheRefCloneHijack func()
type cacheRef struct {
*cacheRefShare
}
func (r *cacheRef) Release(ctx context.Context) error {
if r.main != nil {
r.main.mu.Lock()
defer r.main.mu.Unlock()
}
r.mu.Lock()
defer r.mu.Unlock()
delete(r.refs, r)
if len(r.refs) == 0 {
if cacheRefReleaseHijack != nil {
cacheRefReleaseHijack()
}
return r.release(ctx)
}
return nil
}
const keyCacheDir = "cache-dir"
const cacheDirIndex = keyCacheDir + ":"
func SearchCacheDir(ctx context.Context, store cache.MetadataStore, id string) ([]CacheRefMetadata, error) {
var results []CacheRefMetadata
mds, err := store.Search(ctx, cacheDirIndex+id)
if err != nil {
return nil, err
}
for _, md := range mds {
results = append(results, CacheRefMetadata{md})
}
return results, nil
}
type CacheRefMetadata struct {
cache.RefMetadata
}
func (md CacheRefMetadata) setCacheDirIndex(id string) error {
return md.SetString(keyCacheDir, id, cacheDirIndex+id)
}
func (md CacheRefMetadata) ClearCacheDirIndex() error {
return md.ClearValueAndIndex(keyCacheDir, cacheDirIndex)
}