linux-kernel - [PATCH 05/11] test_hexdump: avoid string truncation warning

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Message-Id: <20240328140512.4148825-6-arnd@kernel.org>
Date: Thu, 28 Mar 2024 15:04:49 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Cc: Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 05/11] 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);
      |                ^~~~~~~~~~~~~~~~~~~~

As far as I can tell, this is harmless here because the truncation is
intentional, but using strscpy_pad() will avoid the warning since gcc
does not (yet) know about it.

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..c9820122af56 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);
+		strscpy_pad(p, data_a, l);
 		p += l;
 	}
 
-- 
2.39.2