Re: Infinite loop in cascade_filter_fn()

["Carlos Martín Nieto" <cmn@elego.de>]

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On Fri, Dec 16, 2011 at 02:01:50PM -0800, Junio C Hamano wrote:
> 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?

Yes we should, thanks for spotting it.

> 
> >  	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;
> >  		}
> 

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