linux-kernel - [PATCH v2 2/2] mm/rodata_test: verify test data is unchanged, rather than non-zero

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Message-ID: <386ffda192eb4a26f68c526c496afd48a5cd87ce.1732016064.git.ptesarik@suse.com>
Date: Tue, 19 Nov 2024 12:37:39 +0100
From: Petr Tesarik <ptesarik@...e.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <kees@...nel.org>,
	Jinbum Park <jinb.park7@...il.com>
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Petr Tesarik <ptesarik@...e.com>
Subject: [PATCH v2 2/2] mm/rodata_test: verify test data is unchanged, rather than non-zero

Verify that the test variable holds the initialization value, rather than
any non-zero value.

Signed-off-by: Petr Tesarik <ptesarik@...e.com>
---
 mm/rodata_test.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/rodata_test.c b/mm/rodata_test.c
index 3b60425d80fe..e7173fcd210c 100644
--- a/mm/rodata_test.c
+++ b/mm/rodata_test.c
@@ -12,7 +12,8 @@
 #include <linux/mm.h>
 #include <asm/sections.h>
 
-static const int rodata_test_data = 0xC3;
+#define TEST_VALUE 0xC3
+static const int rodata_test_data = TEST_VALUE;
 
 void rodata_test(void)
 {
@@ -20,7 +21,7 @@ void rodata_test(void)
 
 	/* test 1: read the value */
 	/* If this test fails, some previous testrun has clobbered the state */
-	if (!READ_ONCE(rodata_test_data)) {
+	if (unlikely(READ_ONCE(rodata_test_data) != TEST_VALUE)) {
 		pr_err("test 1 fails (start data)\n");
 		return;
 	}
@@ -33,7 +34,7 @@ void rodata_test(void)
 	}
 
 	/* test 3: check the value hasn't changed */
-	if (READ_ONCE(rodata_test_data) == zero) {
+	if (unlikely(READ_ONCE(rodata_test_data) != TEST_VALUE)) {
 		pr_err("test data was changed\n");
 		return;
 	}
-- 
2.46.1