linux-kernel - [PATCH v1 3/3] kernel: Fix off-by-one benign bugs

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Message-ID: <f03b6e802662b437468d25b32bf9699875dc210f.1758806023.git.alx@kernel.org>
Date: Thu, 25 Sep 2025 15:20:52 +0200
From: Alejandro Colomar <alx@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Alejandro Colomar <alx@...nel.org>, Marco Elver <elver@...gle.com>, 
	Kees Cook <kees@...nel.org>, Christopher Bazley <chris.bazley.wg14@...il.com>, 
	Alexander Potapenko <glider@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Jann Horn <jannh@...gle.com>, 
	Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Rasmus Villemoes <linux@...musvillemoes.dk>, Michal Hocko <mhocko@...e.com>, 
	Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH v1 3/3] kernel: Fix off-by-one benign bugs

We were wasting a byte due to an off-by-one bug.  s[c]nprintf()
doesn't write more than $2 bytes including the null byte, so trying to
pass 'size-1' there is wasting one byte.

This is essentially the same as the previous commit, in a different
file.

Cc: Marco Elver <elver@...gle.com>
Cc: Kees Cook <kees@...nel.org>
Cc: Christopher Bazley <chris.bazley.wg14@...il.com>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Jann Horn <jannh@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Marco Elver <elver@...gle.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Alejandro Colomar <alx@...nel.org>
---
 kernel/kcsan/kcsan_test.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c
index c2871180edcc..621a60a86b39 100644
--- a/kernel/kcsan/kcsan_test.c
+++ b/kernel/kcsan/kcsan_test.c
@@ -176,7 +176,7 @@ static bool __report_matches(const struct expect_report *r)
 
 	/* Title */
 	cur = expect[0];
-	end = &expect[0][sizeof(expect[0]) - 1];
+	end = ENDOF(expect[0]);
 	cur += scnprintf(cur, end - cur, "BUG: KCSAN: %s in ",
 			 is_assert ? "assert: race" : "data-race");
 	if (r->access[1].fn) {
@@ -200,7 +200,7 @@ static bool __report_matches(const struct expect_report *r)
 
 	/* Access 1 */
 	cur = expect[1];
-	end = &expect[1][sizeof(expect[1]) - 1];
+	end = ENDOF(expect[1]);
 	if (!r->access[1].fn)
 		cur += scnprintf(cur, end - cur, "race at unknown origin, with ");
 
-- 
2.51.0