linux-kernel - [PATCH v2] unicode: don't write -1 after NUL terminator

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Message-Id: <20221103113021.3271-1-Jason@zx2c4.com>
Date:   Thu,  3 Nov 2022 12:30:21 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        krisman@...labora.com, jirislaby@...nel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>, stable@...r.kernel.org
Subject: [PATCH v2] unicode: don't write -1 after NUL terminator

If the intention is to overwrite the first NUL with a -1, s[strlen(s)]
is the first NUL, not s[strlen(s)+1].

Cc: Gabriel Krisman Bertazi <krisman@...labora.com>
Cc: stable@...r.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 fs/unicode/mkutf8data.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/unicode/mkutf8data.c b/fs/unicode/mkutf8data.c
index bc1a7c8b5c8d..61800e0d3226 100644
--- a/fs/unicode/mkutf8data.c
+++ b/fs/unicode/mkutf8data.c
@@ -3194,7 +3194,7 @@ static int normalize_line(struct tree *tree)
 	/* Second test: length-limited string. */
 	s = buf2;
 	/* Replace NUL with a value that will cause an error if seen. */
-	s[strlen(s) + 1] = -1;
+	s[strlen(s)] = -1;
 	t = buf3;
 	if (utf8cursor(&u8c, tree, s))
 		return -1;
-- 
2.38.1