linux-kernel - [PATCH 1/5] [v2] test_hexdump: avoid string truncation warning

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Date: Tue,  9 Apr 2024 16:00:54 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>,
	"Richard Russon" <ldm@...tcap.org>,
	Jens Axboe <axboe@...nel.dk>,
	Robert Moore <robert.moore@...el.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <lenb@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>,
	Lin Ming <ming.m.lin@...el.com>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	linux-ntfs-dev@...ts.sourceforge.net,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	acpica-devel@...ts.linux.dev,
	linux-trace-kernel@...r.kernel.org,
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH 1/5] [v2] test_hexdump: avoid string truncation warning

From: Arnd Bergmann <arnd@...db.de>

gcc can warn when a string is too long to fit into the strncpy()
destination buffer, as it is here depending on the function
arguments:

    inlined from 'test_hexdump_prepare_test.constprop' at /home/arnd/arm-soc/lib/test_hexdump.c:116:3:
include/linux/fortify-string.h:108:33: error: '__builtin_strncpy' output truncated copying between 0 and 32 bytes from a string of length 32 [-Werror=stringop-truncation]
  108 | #define __underlying_strncpy    __builtin_strncpy
      |                                 ^
include/linux/fortify-string.h:187:16: note: in expansion of macro '__underlying_strncpy'
  187 |         return __underlying_strncpy(p, q, size);
      |                ^~~~~~~~~~~~~~~~~~~~

The intention here is to copy exactly 'l' bytes without any padding or
NUL-termination, so the most logical change is to use memcpy(), just as
a previous change adapted the other output from strncpy() to memcpy().

Cc: Justin Stitt <justinstitt@...gle.com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
---
 lib/test_hexdump.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/test_hexdump.c b/lib/test_hexdump.c
index b916801f23a8..fe2682bb21e6 100644
--- a/lib/test_hexdump.c
+++ b/lib/test_hexdump.c
@@ -113,7 +113,7 @@ static void __init test_hexdump_prepare_test(size_t len, int rowsize,
 			*p++ = ' ';
 		} while (p < test + rs * 2 + rs / gs + 1);
 
-		strncpy(p, data_a, l);
+		memcpy(p, data_a, l);
 		p += l;
 	}
 
-- 
2.39.2