fix: release package collection lock in Ubuntu ESM detection (#5336)

Signed-off-by: Sverrir Sigurðsson <svesig@gmail.com>

internal/os/feature_detection.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"regexp"
+	"slices"
 
 	"github.com/anchore/syft/internal"
 	"github.com/anchore/syft/internal/log"
@@ -191,12 +192,9 @@ func hasInstalledESMPackage(packages *pkg.Collection) bool {
 	if packages == nil {
 		return false
 	}
-	for p := range packages.Enumerate(pkg.DebPkg) {
-		if esmVersionPattern.MatchString(p.Version) {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(packages.Sorted(pkg.DebPkg), func(p pkg.Package) bool {
+		return esmVersionPattern.MatchString(p.Version)
+	})
 }
 
 func fileMatchesAny(resolver file.Resolver, location file.Location, patterns ...*regexp.Regexp) (bool, error) {

internal/os/feature_detection_test.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"slices"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 
@@ -232,6 +233,33 @@ func Test_findUbuntuFeatures(t *testing.T) {
 	}
 }
 
+// returning early from Collection.Enumerate leaks its goroutine and read lock, so any later write blocks forever.
+func Test_findUbuntuFeatures_releasesPackageCollectionLock(t *testing.T) {
+	resolver := fixtureResolverForDir(t, "testdata/ubuntu_plain")
+
+	s := sbom.SBOM{}
+	s.Artifacts.LinuxDistribution = &linux.Release{ID: "ubuntu"}
+	s.Artifacts.Packages = pkg.NewCollection(
+		pkg.Package{Name: "openssl", Version: "1.1.1f-1ubuntu2.19+esm1", Type: pkg.DebPkg},
+		pkg.Package{Name: "libcap2", Version: "1:2.32-1ubuntu0.1~esm1", Type: pkg.DebPkg},
+	)
+
+	require.NoError(t, os.DetectFeatures(context.Background(), resolver, sbomsync.NewBuilder(&s)))
+	require.True(t, s.Artifacts.LinuxDistribution.ExtendedSupport)
+
+	added := make(chan struct{})
+	go func() {
+		s.Artifacts.Packages.Add(pkg.Package{Name: "zlib1g", Version: "1:1.2.11.dfsg-2ubuntu1", Type: pkg.DebPkg})
+		close(added)
+	}()
+
+	select {
+	case <-added:
+	case <-time.After(5 * time.Second):
+		t.Fatal("package collection is still read-locked after feature detection")
+	}
+}
+
 // a read error in the apt-source signal must not suppress the ubuntu-advantage status signal; the three
 // signals are meant to be independent fallbacks.
 func Test_findUbuntuFeatures_signalErrorDoesNotSuppressOthers(t *testing.T) {