rootless: improve automatic range split

sort.Search returns the smallest index, so provide the available IDs
in decreasing order.

It fixes an issue when splitting the current mappings over multiple
available IDs.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

2 files changed, 59 insertions, 2 deletions

diff --git a/pkg/rootless/rootless.go b/pkg/rootless/rootless.go
index 0b9d719a9..93b4e2e9f 100644
--- a/pkg/rootless/rootless.go
+++ b/pkg/rootless/rootless.go
@@ -137,7 +137,7 @@ func GetAvailableGids() (int64, error) {
 // It assumes availableMappings is sorted by ID.
 func findIDInMappings(id int64, availableMappings []user.IDMap) *user.IDMap {
 	i := sort.Search(len(availableMappings), func(i int) bool {
-		return availableMappings[i].ID >= id
+		return availableMappings[i].ID <= id
 	})
 	if i < 0 || i >= len(availableMappings) {
 		return nil
@@ -157,7 +157,7 @@ func MaybeSplitMappings(mappings []spec.LinuxIDMapping, availableMappings []user
 	overflow.Size = 0
 	consumed := 0
 	sort.Slice(availableMappings, func(i, j int) bool {
-		return availableMappings[i].ID < availableMappings[j].ID
+		return availableMappings[i].ID > availableMappings[j].ID
 	})
 	for {
 		cur := overflow
diff --git a/pkg/rootless/rootless_test.go b/pkg/rootless/rootless_test.go
index ef574099c..fe9b23cdf 100644
--- a/pkg/rootless/rootless_test.go
+++ b/pkg/rootless/rootless_test.go
@@ -98,4 +98,61 @@ func TestMaybeSplitMappings(t *testing.T) {
 	if !reflect.DeepEqual(newMappings, desiredMappings) {
 		t.Fatal("wrong mappings generated")
 	}
+
+	mappings = []spec.LinuxIDMapping{
+		{
+			ContainerID: 0,
+			HostID:      0,
+			Size:        4,
+		},
+	}
+	desiredMappings = []spec.LinuxIDMapping{
+		{
+			ContainerID: 0,
+			HostID:      0,
+			Size:        1,
+		},
+		{
+			ContainerID: 1,
+			HostID:      1,
+			Size:        1,
+		},
+		{
+			ContainerID: 2,
+			HostID:      2,
+			Size:        1,
+		},
+		{
+			ContainerID: 3,
+			HostID:      3,
+			Size:        1,
+		},
+	}
+	availableMappings = []user.IDMap{
+		{
+			ID:       0,
+			ParentID: 0,
+			Count:    1,
+		},
+		{
+			ID:       1,
+			ParentID: 1,
+			Count:    1,
+		},
+		{
+			ID:       2,
+			ParentID: 2,
+			Count:    1,
+		},
+		{
+			ID:       3,
+			ParentID: 3,
+			Count:    1,
+		},
+	}
+
+	newMappings = MaybeSplitMappings(mappings, availableMappings)
+	if !reflect.DeepEqual(newMappings, desiredMappings) {
+		t.Fatal("wrong mappings generated")
+	}
 }