linux-kernel - [PATCH 4/4] lkdtm: Make arch-specific tests always available

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Message-Id: <20200529200347.2464284-5-keescook@chromium.org>
Date:   Fri, 29 May 2020 13:03:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Prasad Sodagudi <psodagud@...eaurora.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        linux-kselftest@...r.kernel.org,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] lkdtm: Make arch-specific tests always available

I'd like arch-specific tests to XFAIL when on a mismatched architecture
so that we can more easily compare test coverage across all systems.
Lacking kernel configs or CPU features count as a FAIL, not an XFAIL.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/misc/lkdtm/bugs.c               | 34 ++++++++++++++-----------
 drivers/misc/lkdtm/lkdtm.h              |  2 --
 tools/testing/selftests/lkdtm/tests.txt |  1 +
 3 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c
index e1b43f615549..f3fde0759f2c 100644
--- a/drivers/misc/lkdtm/bugs.c
+++ b/drivers/misc/lkdtm/bugs.c
@@ -453,38 +453,42 @@ void lkdtm_DOUBLE_FAULT(void)
 #endif
 }
 
-#ifdef CONFIG_ARM64_PTR_AUTH
+#ifdef CONFIG_ARM64
 static noinline void change_pac_parameters(void)
 {
-	/* Reset the keys of current task */
-	ptrauth_thread_init_kernel(current);
-	ptrauth_thread_switch_kernel(current);
+	if (IS_ENABLED(CONFIG_ARM64_PTR_AUTH)) {
+		/* Reset the keys of current task */
+		ptrauth_thread_init_kernel(current);
+		ptrauth_thread_switch_kernel(current);
+	}
 }
+#endif
 
-#define CORRUPT_PAC_ITERATE	10
 noinline void lkdtm_CORRUPT_PAC(void)
 {
+#ifdef CONFIG_ARM64
+#define CORRUPT_PAC_ITERATE	10
 	int i;
 
+	if (!IS_ENABLED(CONFIG_ARM64_PTR_AUTH))
+		pr_err("FAIL: kernel not built with CONFIG_ARM64_PTR_AUTH\n");
+
 	if (!system_supports_address_auth()) {
-		pr_err("FAIL: arm64 pointer authentication feature not present\n");
+		pr_err("FAIL: CPU lacks pointer authentication feature\n");
 		return;
 	}
 
-	pr_info("Change the PAC parameters to force function return failure\n");
+	pr_info("changing PAC parameters to force function return failure...\n");
 	/*
-	 * Pac is a hash value computed from input keys, return address and
+	 * PAC is a hash value computed from input keys, return address and
 	 * stack pointer. As pac has fewer bits so there is a chance of
 	 * collision, so iterate few times to reduce the collision probability.
 	 */
 	for (i = 0; i < CORRUPT_PAC_ITERATE; i++)
 		change_pac_parameters();
 
-	pr_err("FAIL: %s test failed. Kernel may be unstable from here\n", __func__);
-}
-#else /* !CONFIG_ARM64_PTR_AUTH */
-noinline void lkdtm_CORRUPT_PAC(void)
-{
-	pr_err("FAIL: arm64 pointer authentication config disabled\n");
-}
+	pr_err("FAIL: survived PAC changes! Kernel may be unstable from here\n");
+#else
+	pr_err("XFAIL: this test is arm64-only\n");
 #endif
+}
diff --git a/drivers/misc/lkdtm/lkdtm.h b/drivers/misc/lkdtm/lkdtm.h
index 601a2156a0d4..8878538b2c13 100644
--- a/drivers/misc/lkdtm/lkdtm.h
+++ b/drivers/misc/lkdtm/lkdtm.h
@@ -31,9 +31,7 @@ void lkdtm_CORRUPT_USER_DS(void);
 void lkdtm_STACK_GUARD_PAGE_LEADING(void);
 void lkdtm_STACK_GUARD_PAGE_TRAILING(void);
 void lkdtm_UNSET_SMEP(void);
-#ifdef CONFIG_X86_32
 void lkdtm_DOUBLE_FAULT(void);
-#endif
 void lkdtm_CORRUPT_PAC(void);
 
 /* lkdtm_heap.c */
diff --git a/tools/testing/selftests/lkdtm/tests.txt b/tools/testing/selftests/lkdtm/tests.txt
index 92ca32143ae5..9d266e79c6a2 100644
--- a/tools/testing/selftests/lkdtm/tests.txt
+++ b/tools/testing/selftests/lkdtm/tests.txt
@@ -14,6 +14,7 @@ STACK_GUARD_PAGE_LEADING
 STACK_GUARD_PAGE_TRAILING
 UNSET_SMEP CR4 bits went missing
 DOUBLE_FAULT
+CORRUPT_PAC
 UNALIGNED_LOAD_STORE_WRITE
 #OVERWRITE_ALLOCATION Corrupts memory on failure
 #WRITE_AFTER_FREE Corrupts memory on failure
-- 
2.25.1