linux-kernel - [RFC v6 3/8] sprintf: Add [v]sprintf

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Message-ID: <9348d5df2d9f3a64be70a161f7af39ba30a0edc2.1752193588.git.alx@kernel.org>
Date: Fri, 11 Jul 2025 03:56:51 +0200
From: Alejandro Colomar <alx@...nel.org>
To: linux-mm@...ck.org, linux-hardening@...r.kernel.org
Cc: Alejandro Colomar <alx@...nel.org>, Kees Cook <kees@...nel.org>, 
	Christopher Bazley <chris.bazley.wg14@...il.com>, shadow <~hallyn/shadow@...ts.sr.ht>, 
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	kasan-dev@...glegroups.com, Dmitry Vyukov <dvyukov@...gle.com>, 
	Alexander Potapenko <glider@...gle.com>, Marco Elver <elver@...gle.com>, Christoph Lameter <cl@...ux.com>, 
	David Rientjes <rientjes@...gle.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Roman Gushchin <roman.gushchin@...ux.dev>, Harry Yoo <harry.yoo@...cle.com>, 
	Andrew Clayton <andrew@...ital-domain.net>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Michal Hocko <mhocko@...e.com>, Linus Torvalds <torvalds@...ux-foundation.org>, 
	Al Viro <viro@...iv.linux.org.uk>, Martin Uecker <uecker@...raz.at>, Sam James <sam@...too.org>, 
	Andrew Pinski <pinskia@...il.com>
Subject: [RFC v6 3/8] sprintf: Add [v]sprintf_array()

These macros take the end of the array argument implicitly to avoid
programmer mistakes.  This guarantees that the input is an array, unlike

	snprintf(buf, sizeof(buf), ...);

which is dangerous if the programmer passes a pointer instead of an
array.

These macros are essentially the same as the 2-argument version of
strscpy(), but with a formatted string.

Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: Marco Elver <elver@...gle.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Alejandro Colomar <alx@...nel.org>
---
 include/linux/sprintf.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/sprintf.h b/include/linux/sprintf.h
index 8dfc37713747..bd8174224a4a 100644
--- a/include/linux/sprintf.h
+++ b/include/linux/sprintf.h
@@ -4,6 +4,10 @@
 
 #include <linux/compiler_attributes.h>
 #include <linux/types.h>
+#include <linux/array_size.h>
+
+#define sprintf_array(a, fmt, ...)  sprintf_trunc(a, ARRAY_SIZE(a), fmt, ##__VA_ARGS__)
+#define vsprintf_array(a, fmt, ap)  vsprintf_trunc(a, ARRAY_SIZE(a), fmt, ap)
 
 int num_to_str(char *buf, int size, unsigned long long num, unsigned int width);
 
-- 
2.50.0