linux-kernel - [PATCH] vboxsf: Add __nonstring annotations for unterminated strings

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Message-Id: <20250310222530.work.374-kees@kernel.org>
Date: Mon, 10 Mar 2025 15:25:31 -0700
From: Kees Cook <kees@...nel.org>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Kees Cook <kees@...nel.org>,
	Brahmajit Das <brahmajit.xyz@...il.com>,
	Christian Brauner <brauner@...nel.org>,
	linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] vboxsf: Add __nonstring annotations for unterminated strings

When a character array without a terminating NUL character has a static
initializer, GCC 15's -Wunterminated-string-initialization will only
warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
with __nonstring to and correctly identify the char array as "not a C
string" and thereby eliminate the warning.

This effectively reverts the change in 4e7487245abc ("vboxsf: fix building
with GCC 15"), to add the annotation that has other uses (i.e. warning
if the string is ever used with C string APIs).

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
Cc: Hans de Goede <hdegoede@...hat.com>
Cc: Brahmajit Das <brahmajit.xyz@...il.com>
Cc: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org
Signed-off-by: Kees Cook <kees@...nel.org>
---
 fs/vboxsf/super.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/vboxsf/super.c b/fs/vboxsf/super.c
index 1d94bb784108..0bc96ab6580b 100644
--- a/fs/vboxsf/super.c
+++ b/fs/vboxsf/super.c
@@ -21,8 +21,7 @@
 
 #define VBOXSF_SUPER_MAGIC 0x786f4256 /* 'VBox' little endian */
 
-static const unsigned char VBSF_MOUNT_SIGNATURE[4] = { '\000', '\377', '\376',
-						       '\375' };
+static const unsigned char VBSF_MOUNT_SIGNATURE[4] __nonstring = "\000\377\376\375";
 
 static int follow_symlinks;
 module_param(follow_symlinks, int, 0444);
-- 
2.34.1