Index: tests/sys/vfs/Makefile
===================================================================
--- tests/sys/vfs/Makefile
+++ tests/sys/vfs/Makefile
@@ -4,6 +4,8 @@
 
 TESTSDIR=		${TESTSBASE}/sys/vfs
 
+ATF_TESTS_C+=	lookup_cap_dotdot
+
 PLAIN_TESTS_SH+=	trailing_slash
 
 .include <bsd.test.mk>
Index: tests/sys/vfs/lookup_cap_dotdot.c
===================================================================
--- /dev/null
+++ tests/sys/vfs/lookup_cap_dotdot.c
@@ -0,0 +1,182 @@
+/*-
+ * Copyright (c) 2016 Conrad Meyer <cem@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/capsicum.h>
+#include <sys/sysctl.h>
+#include <sys/stat.h>
+
+#include <atf-c.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void cleanup_dotdot_tests(void);
+
+static const char testdir_template[] = "/tmp/temp.XXXXXX";
+static char testdir[32];
+static int testdir_fd = -1;
+
+static void
+prepare_dotdot_tests(void)
+{
+
+	strcpy(testdir, testdir_template);
+	if (mkdtemp(testdir) == NULL)
+		atf_tc_fail("mkdtemp: %s", strerror(errno));
+	if ((testdir_fd = open(testdir, O_RDONLY)) < 0) {
+		atf_tc_fail_nonfatal("open(%s): %s", testdir, strerror(errno));
+		goto fail;
+	}
+	if (mkdirat(testdir_fd, "b", 0700) < 0) {
+		atf_tc_fail_nonfatal("mkdirat(%s, \"b\"): %s", testdir,
+		    strerror(errno));
+		goto fail;
+	}
+
+	return;
+fail:
+	cleanup_dotdot_tests();
+	atf_tc_fail("Aborting due to previous failure");
+}
+
+static void
+cleanup_dotdot_tests(void)
+{
+
+	if (testdir_fd >= 0) {
+		(void)unlinkat(testdir_fd, "b", AT_REMOVEDIR);
+		close(testdir_fd);
+		testdir_fd = -1;
+	}
+	if (strcmp(testdir, testdir_template) != 0)
+		(void)rmdir(testdir);
+}
+
+static void
+check_capsicum(void)
+{
+	int sval, rc;
+	size_t len;
+
+	len = sizeof(sval);
+	rc = sysctlbyname("kern.features.security_capabilities", &sval, &len,
+	    NULL, 0);
+	if (rc < 0 || sval == 0)
+		atf_tc_skip("System doesn't have Capsicum");
+
+	len = sizeof(sval);
+	rc = sysctlbyname("kern.features.security_capability_mode", &sval,
+	    &len, NULL, 0);
+	if (rc < 0 || sval == 0)
+		atf_tc_skip("System doesn't have Capsicum enabled");
+}
+
+/*
+ * Positive tests
+ */
+ATF_TC_WITH_CLEANUP(lookup_cap_dotdot__basic);
+ATF_TC_HEAD(lookup_cap_dotdot__basic, tc)
+{
+	atf_tc_set_md_var(tc, "require.user", "root");
+	atf_tc_set_md_var(tc, "descr",
+	    "Validate cap-mode (a)/b/.. lookup");
+}
+
+ATF_TC_BODY(lookup_cap_dotdot__basic, tc)
+{
+	cap_rights_t rights;
+	int fd;
+
+	check_capsicum();
+	prepare_dotdot_tests();
+
+	cap_rights_init(&rights, CAP_LOOKUP, CAP_READ);
+	if (cap_rights_limit(testdir_fd, &rights) < 0)
+		atf_tc_fail("cap_rights_limit: %s", strerror(errno));
+
+	fd = openat(testdir_fd, "b/..", O_RDONLY);
+	if (fd < 0)
+		atf_tc_fail("openat(%s, b/../b): %s", testdir,
+		    strerror(errno));
+}
+
+ATF_TC_CLEANUP(lookup_cap_dotdot__basic, tc)
+{
+
+	cleanup_dotdot_tests();
+}
+
+/*
+ * Negative tests
+ */
+ATF_TC_WITH_CLEANUP(lookup_cap_dotdot__negative);
+ATF_TC_HEAD(lookup_cap_dotdot__negative, tc)
+{
+	atf_tc_set_md_var(tc, "require.user", "root");
+	atf_tc_set_md_var(tc, "descr",
+	    "Validate cap-mode (a)/.. lookup fails");
+}
+
+ATF_TC_BODY(lookup_cap_dotdot__negative, tc)
+{
+	cap_rights_t rights;
+	int fd;
+
+	check_capsicum();
+	prepare_dotdot_tests();
+
+	cap_rights_init(&rights, CAP_LOOKUP, CAP_READ);
+	if (cap_rights_limit(testdir_fd, &rights) < 0)
+		atf_tc_fail("cap_rights_limit: %s", strerror(errno));
+
+	errno = 0;
+	fd = openat(testdir_fd, "..", O_RDONLY);
+	if (fd >= 0 || errno != ENOTCAPABLE)
+		atf_tc_fail("openat(%s, ..): %d", testdir, errno);
+
+	errno = 0;
+	fd = openat(testdir_fd, "b/../..", O_RDONLY);
+	if (fd >= 0 || errno != ENOTCAPABLE)
+		atf_tc_fail("openat(%s, ..): %d", testdir, errno);
+}
+
+ATF_TC_CLEANUP(lookup_cap_dotdot__negative, tc)
+{
+
+	cleanup_dotdot_tests();
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+
+	ATF_TP_ADD_TC(tp, lookup_cap_dotdot__basic);
+	ATF_TP_ADD_TC(tp, lookup_cap_dotdot__negative);
+
+	return (atf_no_error());
+}