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Date: Sat, 08 Aug 2009 15:01:29 +0200
From: Alexander Koeppe <format_c@online.de>
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To: roel.kluin@gmail.com
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Subject: Re: [PATCH] fat: Read buffer overflow
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Roel Kluin schrieb:
> If len is less or equal to 0, this results in a read of s[-1].
> 
> Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
> ---
> diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
> index 6f27853..114ff6d 100644
> --- a/fs/fat/namei_vfat.c
> +++ b/fs/fat/namei_vfat.c
> @@ -202,6 +202,9 @@ static inline int vfat_is_used_badchars(const wchar_t *s, int len)
>  {
>  	int i;
>  
> +	if (len <= 0)
> +		return -EINVAL;
> +
>  	for (i = 0; i < len; i++)
>  		if (vfat_bad_char(s[i]))
>  			return -EINVAL;
> --
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This seem to be a bit redundant code.
If len is 0 or less, the loop won't iterate even one time and hence
not read outside the buffer.
The only advantage is, that re function signals the invalid argument.

-- A.Koeppe