linux-kernel - Re: [PATCH] unicode: don't write -1 after NULL terminator

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Message-ID: <79db9616-a2ee-9a1a-9a35-b82f65b6d15e@kernel.org>
Date:   Thu, 3 Nov 2022 08:00:44 +0100
From:   Jiri Slaby <jirislaby@...nel.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        krisman@...labora.com
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH] unicode: don't write -1 after NULL terminator

On 03. 11. 22, 2:24, Jason A. Donenfeld wrote:
> If the intention is to overwrite the first NULL with a -1, s[strlen(s)]
> is the first NULL, not s[strlen(s)+1].

This caught my attention. You mix NULL (void *) with NUL (\0) in the 
changelog & subject. That occurs rather confusing to me.

> 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;

-- 
js
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