linux-kernel - [PATCH] xen/mcelog: Add __nonstring annotations for unterminated strings

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Message-Id: <20250310222234.work.473-kees@kernel.org>
Date: Mon, 10 Mar 2025 15:22:38 -0700
From: Kees Cook <kees@...nel.org>
To: Juergen Gross <jgross@...e.com>
Cc: Kees Cook <kees@...nel.org>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
	xen-devel@...ts.xenproject.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] xen/mcelog: 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.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>
Cc: xen-devel@...ts.xenproject.org
Signed-off-by: Kees Cook <kees@...nel.org>
---
 include/xen/interface/xen-mca.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/xen/interface/xen-mca.h b/include/xen/interface/xen-mca.h
index 464aa6b3a5f9..1c9afbe8cc26 100644
--- a/include/xen/interface/xen-mca.h
+++ b/include/xen/interface/xen-mca.h
@@ -372,7 +372,7 @@ struct xen_mce {
 #define XEN_MCE_LOG_LEN 32
 
 struct xen_mce_log {
-	char signature[12]; /* "MACHINECHECK" */
+	char signature[12] __nonstring; /* "MACHINECHECK" */
 	unsigned len;	    /* = XEN_MCE_LOG_LEN */
 	unsigned next;
 	unsigned flags;
-- 
2.34.1