Add basic tests for the kpkeys_hardened_pgtables feature: try to
perform a direct write to current->{cred,real_cred} and ensure it
fails.
Signed-off-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
---
mm/Makefile | 1 +
mm/kpkeys_hardened_cred_test.c | 42 ++++++++++++++++++++++++++++++++++
security/Kconfig.hardening | 11 +++++++++
3 files changed, 54 insertions(+)
create mode 100644 mm/kpkeys_hardened_cred_test.c
diff --git a/mm/Makefile b/mm/Makefile
index f7263b7f45b8..2024226902d4 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -149,3 +149,4 @@ obj-$(CONFIG_TMPFS_QUOTA) += shmem_quota.o
obj-$(CONFIG_PT_RECLAIM) += pt_reclaim.o
obj-$(CONFIG_KPKEYS_HARDENED_PGTABLES) += kpkeys_hardened_pgtables.o
obj-$(CONFIG_KPKEYS_HARDENED_PGTABLES_TEST) += kpkeys_hardened_pgtables_test.o
+obj-$(CONFIG_KPKEYS_HARDENED_CRED_TEST) += kpkeys_hardened_cred_test.o
diff --git a/mm/kpkeys_hardened_cred_test.c b/mm/kpkeys_hardened_cred_test.c
new file mode 100644
index 000000000000..46048098f99d
--- /dev/null
+++ b/mm/kpkeys_hardened_cred_test.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <kunit/test.h>
+#include <linux/sched.h>
+
+static void write_cred(struct kunit *test)
+{
+ long zero = 0;
+ int ret;
+
+ ret = copy_to_kernel_nofault((unsigned long *)current->cred, &zero, sizeof(zero));
+ KUNIT_EXPECT_EQ_MSG(test, ret, -EFAULT,
+ "Write to current->cred wasn't prevented");
+
+ ret = copy_to_kernel_nofault((unsigned long *)current->real_cred, &zero, sizeof(zero));
+ KUNIT_EXPECT_EQ_MSG(test, ret, -EFAULT,
+ "Write to current->real_cred wasn't prevented");
+}
+
+static int kpkeys_hardened_cred_suite_init(struct kunit_suite *suite)
+{
+ if (!arch_kpkeys_enabled()) {
+ pr_err("Cannot run kpkeys_hardened_cred tests: kpkeys are not supported\n");
+ return 1;
+ }
+
+ return 0;
+}
+
+static struct kunit_case kpkeys_hardened_cred_test_cases[] = {
+ KUNIT_CASE(write_cred),
+ {}
+};
+
+static struct kunit_suite kpkeys_hardened_cred_test_suite = {
+ .name = "Hardened credentials using kpkeys",
+ .test_cases = kpkeys_hardened_cred_test_cases,
+ .suite_init = kpkeys_hardened_cred_suite_init,
+};
+kunit_test_suite(kpkeys_hardened_cred_test_suite);
+
+MODULE_DESCRIPTION("Tests for the kpkeys_hardened_cred feature");
+MODULE_LICENSE("GPL");
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 1af3a9dae645..9b0563a03ab4 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -338,6 +338,17 @@ config KPKEYS_HARDENED_CRED
This option has no effect if the system does not support
kernel pkeys.
+config KPKEYS_HARDENED_CRED_TEST
+ tristate "KUnit tests for kpkeys_hardened_cred" if !KUNIT_ALL_TESTS
+ depends on KPKEYS_HARDENED_CRED
+ depends on KUNIT
+ default KUNIT_ALL_TESTS
+ help
+ Enable this option to check that the kpkeys_hardened_cred feature
+ functions as intended, i.e. prevents arbitrary writes to live credentials.
+
+ If unsure, say N.
+
endmenu
config CC_HAS_RANDSTRUCT
--
2.47.0
