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From: Thorsten Blum <thorsten.blum@linux.dev>
To: Andrew Morton <akpm@linux-foundation.org>,
	Kees Cook <kees@kernel.org>, Andy Shevchenko <andy@kernel.org>
Cc: Thorsten Blum <thorsten.blum@linux.dev>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: [PATCH] string: use strnlen in strlcat
Date: Thu, 30 Apr 2026 22:50:53 +0200	[thread overview]
Message-ID: <20260430205050.400822-4-thorsten.blum@linux.dev> (raw)

Use strnlen() to limit the destination scan to the provided buffer size.
Remove the redundant comment.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
 lib/string.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/lib/string.c b/lib/string.c
index b632c71df1a5..7b67e186d898 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -251,12 +251,11 @@ EXPORT_SYMBOL(strncat);
 #ifndef __HAVE_ARCH_STRLCAT
 size_t strlcat(char *dest, const char *src, size_t count)
 {
-	size_t dsize = strlen(dest);
+	size_t dsize = strnlen(dest, count);
 	size_t len = strlen(src);
 	size_t res = dsize + len;
 
-	/* This would be a bug */
-	BUG_ON(dsize >= count);
+	BUG_ON(dsize == count);
 
 	dest += dsize;
 	count -= dsize;

             reply	other threads:[~2026-04-30 20:53 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-04-30 20:50 Thorsten Blum [this message]
2026-05-01  8:55 ` [PATCH] string: use strnlen in strlcat Andy Shevchenko
2026-05-02  8:37   ` Andy Shevchenko
2026-05-04 12:26     ` Manuel Ebner
2026-05-04 12:52       ` Andy Shevchenko

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