libpod: correctly map UID/GID for existing dirs

if the target mount path already exists and the container uses a user
namespace, correctly map the target UID/GID to the host values before
attempting a chown.

Closes: containers#21608

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

libpod/container_internal_common.go

@@ -2865,7 +2865,22 @@ func (c *Container) fixVolumePermissions(v *ContainerNamedVolume) error {
 		st, err := os.Lstat(filepath.Join(c.state.Mountpoint, v.Dest))
 		if err == nil {
 			if stat, ok := st.Sys().(*syscall.Stat_t); ok {
-				if err := idtools.SafeLchown(mountPoint, int(stat.Uid), int(stat.Gid)); err != nil {
+				uid, gid := int(stat.Uid), int(stat.Gid)
+
+				if c.config.IDMappings.UIDMap != nil {
+					p := idtools.IDPair{
+						UID: uid,
+						GID: gid,
+					}
+					mappings := idtools.NewIDMappingsFromMaps(c.config.IDMappings.UIDMap, c.config.IDMappings.GIDMap)
+					newUID, newGID, err := mappings.ToContainer(p)
+					if err != nil {
+						return fmt.Errorf("mapping user %d:%d: %w", uid, gid, err)
+					}
+					uid, gid = newUID, newGID
+				}
+
+				if err := idtools.SafeLchown(mountPoint, uid, gid); err != nil {
 					return err
 				}
 			}

test/e2e/run_userns_test.go

@@ -105,6 +105,22 @@ var _ = Describe("Podman UserNS support", func() {
 		Expect(session.OutputToString()).To(ContainSubstring("#0:0#"))
 	})
 
+	It("podman uidmapping and gidmapping with an idmapped volume on existing directory", func() {
+		SkipIfRunc(podmanTest, "Test not supported yet with runc (issue 17433, wontfix)")
+		SkipOnOSVersion("fedora", "36")
+		// The directory /mnt already exists in the image
+		session := podmanTest.Podman([]string{"run", "--uidmap=0:1:500", "--gidmap=0:200:5000", "-v", "my-foo-volume:/mnt:Z,idmap", "alpine", "stat", "-c", "#%u:%g#", "/mnt"})
+		session.WaitWithDefaultTimeout()
+		if strings.Contains(session.ErrorToString(), "Operation not permitted") {
+			Skip("not sufficiently privileged")
+		}
+		if strings.Contains(session.ErrorToString(), "Invalid argument") {
+			Skip("the file system doesn't support idmapped mounts")
+		}
+		Expect(session).Should(ExitCleanly())
+		Expect(session.OutputToString()).To(ContainSubstring("#0:0#"))
+	})
+
 	It("podman uidmapping and gidmapping --net=host", func() {
 		session := podmanTest.Podman([]string{"run", "--net=host", "--uidmap=0:1:5000", "--gidmap=0:200:5000", "alpine", "echo", "hello"})
 		session.WaitWithDefaultTimeout()