linux-hardening - [PATCH v2] md/bcache: Mark _

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Message-Id: <20250418202130.it.887-kees@kernel.org>
Date: Fri, 18 Apr 2025 13:21:36 -0700
From: Kees Cook <kees@...nel.org>
To: Coly Li <colyli@...nel.org>
Cc: Kees Cook <kees@...nel.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Ard Biesheuvel <ardb@...nel.org>,
	linux-bcache@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH v2] md/bcache: Mark __nonstring look-up table

GCC 15's new -Wunterminated-string-initialization notices that the 16
character lookup table "zero_uuid" (which is not used as a C-String)
needs to be marked as "nonstring":

drivers/md/bcache/super.c: In function 'uuid_find_empty':
drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
  549 |         static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
      |                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Add the annotation (since it is not used as a C-String), and switch the
initializer to an array of bytes.

Signed-off-by: Kees Cook <kees@...nel.org>
---
 v2: use byte array initializer (colyli)
 v1: https://lore.kernel.org/all/20250416220135.work.394-kees@kernel.org/
Cc: Coly Li <colyli@...nel.org>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: linux-bcache@...r.kernel.org
---
 drivers/md/bcache/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index e42f1400cea9..a76ce92502ed 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -546,7 +546,8 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
 
 static struct uuid_entry *uuid_find_empty(struct cache_set *c)
 {
-	static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
+	static const char zero_uuid[] __nonstring =
+		{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
 
 	return uuid_find(c, zero_uuid);
 }
-- 
2.34.1