fix

For pull_request_target tasks, use the pull request head SHA from the event payload as the default checkout ref so actions/checkout resolves the submitted PR content instead of the base branch tip.

Fixes: https://gitea.com/gitea/runner/issues/563

Co-Authored-By: GPT-5 Codex <codex@openai.com>

Dockerfile

@@ -17,14 +17,14 @@ RUN make clean && make build
 ### DIND VARIANT
 #
 #
-FROM docker:29.6.0-dind AS dind
+FROM docker:29.6.1-dind AS dind
 
 ARG VERSION=dev
 
 LABEL org.opencontainers.image.source="https://gitea.com/gitea/runner"
 LABEL org.opencontainers.image.version="${VERSION}"
 
-RUN apk add --no-cache s6 bash git tzdata
+RUN apk add --no-cache s6 bash git tzdata nftables
 
 COPY --from=builder /opt/src/runner/gitea-runner /usr/local/bin/gitea-runner
 COPY scripts/run.sh /usr/local/bin/run.sh
@@ -37,7 +37,7 @@ ENTRYPOINT ["s6-svscan","/etc/s6"]
 ### DIND-ROOTLESS VARIANT
 #
 #
-FROM docker:29.6.0-dind-rootless AS dind-rootless
+FROM docker:29.6.1-dind-rootless AS dind-rootless
 
 ARG VERSION=dev
 
@@ -45,7 +45,7 @@ LABEL org.opencontainers.image.source="https://gitea.com/gitea/runner"
 LABEL org.opencontainers.image.version="${VERSION}"
 
 USER root
-RUN apk add --no-cache s6 bash git tzdata
+RUN apk add --no-cache s6 bash git tzdata nftables
 
 COPY --from=builder /opt/src/runner/gitea-runner /usr/local/bin/gitea-runner
 COPY scripts/run.sh /usr/local/bin/run.sh

act/runner/action_composite.go

@@ -8,6 +8,7 @@ import (
 	"context"
 	"errors"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 
@@ -85,6 +86,19 @@ func newCompositeRunContext(ctx context.Context, parent *RunContext, step action
 	return compositerc
 }
 
+// appendUniqueMasks appends the masks from src to dst, skipping any mask that
+// is already present in dst. This prevents the parent RunContext's Masks slice
+// from growing exponentially when composite actions are nested or repeated,
+// since each composite RunContext is seeded with its parent's masks.
+func appendUniqueMasks(dst, src []string) []string {
+	for _, m := range src {
+		if !slices.Contains(dst, m) {
+			dst = append(dst, m)
+		}
+	}
+	return dst
+}
+
 func execAsComposite(step actionStep) common.Executor {
 	rc := step.getRunContext()
 	action := step.getActionModel()
@@ -110,7 +124,11 @@ func execAsComposite(step actionStep) common.Executor {
 			}, eval.Interpolate(ctx, output.Value))
 		}
 
-		rc.Masks = append(rc.Masks, compositeRC.Masks...)
+		// compositeRC.Masks is seeded with rc.Masks (see newCompositeRunContext)
+		// and may have additional masks appended while the composite action runs.
+		// Only append masks that are not already present, otherwise nested or
+		// repeated composite actions grow rc.Masks exponentially.
+		rc.Masks = appendUniqueMasks(rc.Masks, compositeRC.Masks)
 		rc.ExtraPath = compositeRC.ExtraPath
 		// compositeRC.Env is dirty, contains INPUT_ and merged step env, only rely on compositeRC.GlobalEnv
 		mergeIntoMap := mergeIntoMapCaseSensitive

act/runner/action_composite_test.go

@@ -0,0 +1,70 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package runner
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAppendUniqueMasks(t *testing.T) {
+	tests := []struct {
+		name string
+		dst  []string
+		src  []string
+		want []string
+	}{
+		{
+			name: "appends new masks",
+			dst:  []string{"a"},
+			src:  []string{"b", "c"},
+			want: []string{"a", "b", "c"},
+		},
+		{
+			name: "skips masks already present",
+			dst:  []string{"a", "b"},
+			src:  []string{"a", "b"},
+			want: []string{"a", "b"},
+		},
+		{
+			name: "deduplicates within src",
+			dst:  []string{"a"},
+			src:  []string{"b", "b", "a"},
+			want: []string{"a", "b"},
+		},
+		{
+			name: "empty src leaves dst unchanged",
+			dst:  []string{"a"},
+			src:  nil,
+			want: []string{"a"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, appendUniqueMasks(tt.dst, tt.src))
+		})
+	}
+}
+
+// TestAppendUniqueMasksNoExponentialGrowth reproduces the exponential growth of
+// the parent's Masks slice observed with nested/repeated composite actions. A
+// composite RunContext is seeded with its parent's masks and the whole seeded
+// slice was previously appended back into the parent, doubling its length on
+// every composite action.
+func TestAppendUniqueMasksNoExponentialGrowth(t *testing.T) {
+	parentMasks := []string{"secret"}
+
+	for range 20 {
+		// compositeRC.Masks starts as a copy of the parent's masks (it is
+		// seeded with parent.Masks in newCompositeRunContext).
+		compositeMasks := make([]string, len(parentMasks))
+		copy(compositeMasks, parentMasks)
+
+		parentMasks = appendUniqueMasks(parentMasks, compositeMasks)
+	}
+
+	assert.Equal(t, []string{"secret"}, parentMasks)
+}

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/containerd/errdefs v1.0.0
 	github.com/creack/pty v1.1.24
 	github.com/distribution/reference v0.6.0
-	github.com/docker/cli v29.6.0+incompatible
+	github.com/docker/cli v29.6.1+incompatible
 	github.com/docker/go-connections v0.7.0
 	github.com/go-git/go-billy/v5 v5.9.0
 	github.com/go-git/go-git/v5 v5.19.1

go.sum

@@ -51,6 +51,8 @@ github.com/docker/cli v29.5.3+incompatible h1:nbEFfz774vBwQ5KRYv7c/AghjReqnGISvr
 github.com/docker/cli v29.5.3+incompatible/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
 github.com/docker/cli v29.6.0+incompatible h1:nw9himxMMZ7eIeherJNlKQq+acnlzGgHd+4uf10QRSc=
 github.com/docker/cli v29.6.0+incompatible/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
+github.com/docker/cli v29.6.1+incompatible h1:oO7F4nn3Ovr/5TlfTUWFbMwBSS/B7Xs6Epv26gBrUP8=
+github.com/docker/cli v29.6.1+incompatible/go.mod h1:JLrzqnKDaYBop7H2jaqPtU4hHvMKP+vjCwu2uszcLI8=
 github.com/docker/docker-credential-helpers v0.9.6 h1:cT2PbRPSlnMmNTfT2TDMXRyQ1KMWHG7xoTLBcn1ZNv0=
 github.com/docker/docker-credential-helpers v0.9.6/go.mod h1:v1S+hepowrQXITkEfw6o4+BMbGot02wiKpzWhGUZK6c=
 github.com/docker/go-connections v0.7.0 h1:6SsRfJddP22WMrCkj19x9WKjEDTB+ahsdiGYf0mN39c=

internal/app/run/runner.go

@@ -366,6 +366,7 @@ func (r *Runner) run(ctx context.Context, task *runnerv1.Task, reporter *report.
 	} else if t := task.Secrets["GITHUB_TOKEN"]; t != "" {
 		preset.Token = t
 	}
+	applyPullRequestTargetCheckoutContext(preset)
 
 	if actionsIDTokenRequestURL := taskContext["actions_id_token_request_url"].GetStringValue(); actionsIDTokenRequestURL != "" {
 		envs["ACTIONS_ID_TOKEN_REQUEST_URL"] = actionsIDTokenRequestURL
@@ -574,6 +575,41 @@ func postInternalCache(url, secret string, body map[string]string) error {
 	return nil
 }
 
+func applyPullRequestTargetCheckoutContext(preset *model.GithubContext) {
+	if preset == nil || preset.EventName != "pull_request_target" {
+		return
+	}
+	headSHA := nestedString(preset.Event, "pull_request", "head", "sha")
+	if headSHA == "" {
+		return
+	}
+	preset.Sha = headSHA
+	preset.Ref = headSHA
+	if headRef := nestedString(preset.Event, "pull_request", "head", "ref"); headRef != "" {
+		preset.HeadRef = headRef
+		preset.RefName = headRef
+	}
+}
+
+func nestedString(m map[string]any, keys ...string) string {
+	var current any = m
+	for _, key := range keys {
+		next, ok := current.(map[string]any)
+		if !ok {
+			return ""
+		}
+		current, ok = next[key]
+		if !ok {
+			return ""
+		}
+	}
+	value := current.(string)
+	if value == "" {
+		return ""
+	}
+	return value
+}
+
 func (r *Runner) RunningCount() int64 {
 	return r.runningCount.Load()
 }

internal/app/run/runner_test.go

@@ -7,6 +7,7 @@ import (
 	"context"
 	"testing"
 
+	"gitea.com/gitea/runner/act/model"
 	clientmocks "gitea.com/gitea/runner/internal/pkg/client/mocks"
 	"gitea.com/gitea/runner/internal/pkg/config"
 	"gitea.com/gitea/runner/internal/pkg/ver"
@@ -92,6 +93,67 @@ func TestNewRunnerInitializesLabelsAndEnvironment(t *testing.T) {
 	require.Nil(t, r.cacheHandler)
 }
 
+func TestApplyPullRequestTargetCheckoutContextUsesHeadSHA(t *testing.T) {
+	preset := &model.GithubContext{
+		EventName: "pull_request_target",
+		Sha:       "base-sha",
+		Ref:       "refs/heads/main",
+		RefName:   "main",
+		HeadRef:   "feature",
+		Event: map[string]any{
+			"pull_request": map[string]any{
+				"head": map[string]any{
+					"sha": "head-sha",
+					"ref": "contributor-branch",
+				},
+			},
+		},
+	}
+
+	applyPullRequestTargetCheckoutContext(preset)
+
+	require.Equal(t, "head-sha", preset.Sha)
+	require.Equal(t, "head-sha", preset.Ref)
+	require.Equal(t, "contributor-branch", preset.RefName)
+	require.Equal(t, "contributor-branch", preset.HeadRef)
+}
+
+func TestApplyPullRequestTargetCheckoutContextNoOpsWithoutHeadSHA(t *testing.T) {
+	preset := &model.GithubContext{
+		EventName: "pull_request_target",
+		Sha:       "base-sha",
+		Ref:       "refs/heads/main",
+		RefName:   "main",
+		Event:     map[string]any{},
+	}
+
+	applyPullRequestTargetCheckoutContext(preset)
+
+	require.Equal(t, "base-sha", preset.Sha)
+	require.Equal(t, "refs/heads/main", preset.Ref)
+	require.Equal(t, "main", preset.RefName)
+}
+
+func TestApplyPullRequestTargetCheckoutContextNoOpsForOtherEvents(t *testing.T) {
+	preset := &model.GithubContext{
+		EventName: "pull_request",
+		Sha:       "merge-sha",
+		Ref:       "refs/pull/1/merge",
+		Event: map[string]any{
+			"pull_request": map[string]any{
+				"head": map[string]any{
+					"sha": "head-sha",
+				},
+			},
+		},
+	}
+
+	applyPullRequestTargetCheckoutContext(preset)
+
+	require.Equal(t, "merge-sha", preset.Sha)
+	require.Equal(t, "refs/pull/1/merge", preset.Ref)
+}
+
 func taskWithDefaultActionsURL(url string) *runnerv1.Task {
 	return &runnerv1.Task{
 		Context: &structpb.Struct{