Re: Infinite loop in cascade_filter_fn()

[Junio C Hamano <gitster@pobox.com>]

Carlos Martín Nieto <cmn@elego.de> writes:

> Subject: [PATCHv2] convert: track state in LF-to-CRLF filter
>
> There may not be enough space to store CRLF in the output. If we don't
> fill the buffer, then the filter will keep getting called with the same
> short buffer and will loop forever.
>
> Instead, always store the CR and record whether there's a missing LF
> if so we store it in the output buffer the next time the function gets
> called.
>
> Reported-by: Henrik Grubbström <grubba@roxen.com>
> Signed-off-by: Carlos Martín Nieto <cmn@elego.de>
> ---
>  convert.c |   50 +++++++++++++++++++++++++++++++++++++-------------
>  1 files changed, 37 insertions(+), 13 deletions(-)
>
> diff --git a/convert.c b/convert.c
> index 86e9c29..1c91409 100644
> --- a/convert.c
> +++ b/convert.c
> @@ -876,24 +876,39 @@ int is_null_stream_filter(struct stream_filter *filter)
>  /*
>   * LF-to-CRLF filter
>   */
> +
> +struct lf_to_crlf_filter {
> +	struct stream_filter filter;
> +	int want_lf;
> +};
> +
>  static int lf_to_crlf_filter_fn(struct stream_filter *filter,
>  				const char *input, size_t *isize_p,
>  				char *output, size_t *osize_p)
>  {
> -	size_t count;
> +	size_t count, o = 0;
> +	struct lf_to_crlf_filter *lfcrlf = (struct lf_to_crlf_filter *) filter;
> +
> +	/* Output a pending LF if we need to */
> +	if (lfcrlf->want_lf) {
> +		output[o++] = '\n';
> +		lfcrlf->want_lf = 0;
> +	}
>  
>  	if (!input)
> -		return 0; /* we do not keep any states */
> +		return 0; /* We've already dealt with the state */
> +

Shouldn't we be decrementing *osize_p by 'o' to signal that we used that
many bytes in the output buffer here before returning to the caller?

>  	count = *isize_p;
>  	if (count) {
> -		size_t i, o;
> -		for (i = o = 0; o < *osize_p && i < count; i++) {
> +		size_t i;
> +		for (i = 0; o < *osize_p && i < count; i++) {
>  			char ch = input[i];
>  			if (ch == '\n') {
> -				if (o + 1 < *osize_p)
> -					output[o++] = '\r';
> -				else
> -					break;
> +				output[o++] = '\r';
> +				if (o >= *osize_p) {
> +					lfcrlf->want_lf = 1;
> +					continue; /* We need to increase i */
> +				}
>  			}
>  			output[o++] = ch;
>  		}