libct: skip mount for duplicate masked paths

Co-authored-by: Davanum Srinivas <davanum@gmail.com>
Refactored-by: lifubang <lifubang@acmcoder.com>
Signed-off-by: lifubang <lifubang@acmcoder.com>
(cherry picked from commit abf70bab63)
Signed-off-by: lifubang <lifubang@acmcoder.com>

libcontainer/rootfs_linux.go

@@ -1348,6 +1348,7 @@ func maskPaths(paths []string, mountLabel string) error {
 	procSelfFd, closer := utils.ProcThreadSelf("fd/")
 	defer closer()
 
+	maskedPaths := make(map[string]struct{})
 	for _, path := range paths {
 		// Open the target path; skip if it doesn't exist.
 		dstFh, err := os.OpenFile(path, unix.O_PATH|unix.O_CLOEXEC, 0)
@@ -1362,6 +1363,14 @@ func maskPaths(paths []string, mountLabel string) error {
 			dstFh.Close()
 			return fmt.Errorf("can't mask path %q: %w", path, err)
 		}
+		// skip duplicate masked paths.
+		cleanPath := pathrs.LexicallyCleanPath(path)
+		if _, ok := maskedPaths[cleanPath]; ok {
+			dstFh.Close()
+			continue
+		}
+		maskedPaths[cleanPath] = struct{}{}
+
 		var dstType string
 		if st.IsDir() {
 			// Destination is a directory: bind mount a ro tmpfs over it.

tests/integration/mask.bats

@@ -55,6 +55,20 @@ function teardown() {
 	[[ "${output}" == *"Operation not permitted"* ]]
 }
 
+@test "mask paths [duplicate paths]" {
+	update_config '(.. | select(.maskedPaths? != null)) .maskedPaths += ["/testdir", "/testfile"]'
+	runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox
+	[ "$status" -eq 0 ]
+
+	runc exec test_busybox sh -c "mount | grep /testdir -c"
+	[ "$status" -eq 0 ]
+	[[ "${output}" == "1" ]]
+
+	runc exec test_busybox sh -c "mount | grep /testfile -c"
+	[ "$status" -eq 0 ]
+	[[ "${output}" == "1" ]]
+}
+
 @test "mask paths [prohibit symlink /proc]" {
 	ln -s /symlink rootfs/proc
 	runc run -d --console-socket "$CONSOLE_SOCKET" test_busybox