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[v0.27] forwarder: fix concurrent map write panic in the gateway forwarder #6482

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Merged
tonistiigi merged 1 commit into from
Jan 21, 2026
+32 −20
Merged

[v0.27] forwarder: fix concurrent map write panic in the gateway forwarder #6482

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52 changes: 32 additions & 20 deletions frontend/gateway/forwarder/forward.go
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Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,9 @@ type BridgeClient struct {
buildOpts client.BuildOpts
ctrs []client.Container
executor executor.Executor
mounts map[string]snapshot.Mounter

mounts map[string]snapshot.Mounter
mountsMu sync.Mutex
}

func (c *BridgeClient) Solve(ctx context.Context, req client.SolveRequest) (*client.Result, error) {
Expand Down Expand Up @@ -215,9 +217,7 @@ func (c *BridgeClient) discard(err error) {
ctr.Release(context.TODO())
}

for _, mount := range c.mounts {
mount.Unmount()
}
c.discardMounts()

for id, workerRef := range c.workerRefByID {
workerRef.ImmutableRef.Release(context.TODO())
Expand All @@ -235,6 +235,16 @@ func (c *BridgeClient) discard(err error) {
}
}

func (c *BridgeClient) discardMounts() {
c.mountsMu.Lock()
defer c.mountsMu.Unlock()

for _, mount := range c.mounts {
mount.Unmount()
}
c.mounts = nil
}

func (c *BridgeClient) Warn(ctx context.Context, dgst digest.Digest, msg string, opts client.WarnOpts) error {
return c.FrontendLLBBridge.Warn(ctx, dgst, msg, opts)
}
Expand Down Expand Up @@ -388,26 +398,28 @@ func (r *ref) StatFile(ctx context.Context, req client.StatRequest) (*fstypes.St

func (r *ref) getMounter(ctx context.Context) (snapshot.Mounter, error) {
id := r.resultProxy.ID()
if mounter, ok := r.c.mounts[id]; ok {
return mounter, nil
}

rr, err := r.resultProxy.Result(ctx)
if err != nil {
return nil, r.c.wrapSolveError(err)
}
ref, ok := rr.Sys().(*worker.WorkerRef)
r.c.mountsMu.Lock()
defer r.c.mountsMu.Unlock()

mounter, ok := r.c.mounts[id]
if !ok {
return nil, errors.Errorf("invalid ref: %T", rr.Sys())
}
rr, err := r.resultProxy.Result(ctx)
if err != nil {
return nil, r.c.wrapSolveError(err)
}
ref, ok := rr.Sys().(*worker.WorkerRef)
if !ok {
return nil, errors.Errorf("invalid ref: %T", rr.Sys())
}

mountable, err := ref.ImmutableRef.Mount(ctx, true, r.session)
if err != nil {
return nil, err
mountable, err := ref.ImmutableRef.Mount(ctx, true, r.session)
if err != nil {
return nil, err
}
mounter = snapshot.LocalMounter(mountable)
r.c.mounts[id] = mounter
}
mounter := snapshot.LocalMounter(mountable)

r.c.mounts[id] = mounter
return mounter, nil
}

Expand Down