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From: Taylor Blau <me@ttaylorr.com>
To: Jeff King <peff@peff.net>
Cc: Junio C Hamano <gitster@pobox.com>, git@vger.kernel.org
Subject: Re: [PATCH 6/6] config: reject parsing of files over INT_MAX
Date: Sun, 12 Apr 2020 18:47:24 -0600	[thread overview]
Message-ID: <20200413004724.GB55122@syl.local> (raw)
In-Reply-To: <20200410221549.GA2078378@coredump.intra.peff.net>

On Fri, Apr 10, 2020 at 06:15:49PM -0400, Jeff King wrote:
> On Fri, Apr 10, 2020 at 03:04:31PM -0700, Junio C Hamano wrote:
>
> > Jeff King <peff@peff.net> writes:
> >
> > > So given the fact that these are insane cases which we have no need to
> > > support, the weird behavior from feeding the results to printf even if
> > > the code is careful, and the possibility of uncareful code introducing
> > > its own integer truncation issues, let's just declare INT_MAX as a limit
> > > for parsing config files.
> >
> > Makes sense.
> >
> > > +	if (c != EOF && ++cf->total_len > INT_MAX) {
> >
> > Would this work correctly if size_t is uint?  Sure, as int-max would
> > fit within it.  And of course if size_t is wider than uint, there is
> > no problem in this comparison.
>
> Good question, but yeah, I think it's right.
>
> Another method would be to do:
>
>   if (cf->total_len >= INT_MAX)
>
> _before_ reading any character. We'd have to remember to increment
> total_len then (I suppose we could do it preemptively; as long as people
> don't try to read EOF from us over and over again it would never move
> again).
>
> I also considered making the limit much lower than INT_MAX because
> really, who needs even a 1GB config file? :)

;). Making it lower than INT_MAX moves us into the territory of deciding
what is an "appropriately" sized config file, which I'd rather not do.
At least we can blame INT_MAX if someone has a too-large config file.

> -Peff

Thanks,
Taylor

  reply	other threads:[~2020-04-13  0:47 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-10 19:42 [PATCH 0/6] better handling of gigantic config files Jeff King
2020-04-10 19:43 ` [PATCH 1/6] remote: drop auto-strlen behavior of make_branch() and make_rewrite() Jeff King
2020-04-10 21:44   ` Junio C Hamano
2020-04-10 19:44 ` [PATCH 2/6] parse_config_key(): return subsection len as size_t Jeff King
2020-04-10 19:44 ` [PATCH 3/6] config: drop useless length variable in write_pair() Jeff King
2020-04-10 21:51   ` Junio C Hamano
2020-04-10 19:46 ` [PATCH 4/6] git_config_parse_key(): return baselen as size_t Jeff King
2020-04-10 19:47 ` [PATCH 5/6] config: use size_t to store parsed variable baselen Jeff King
2020-04-10 19:50 ` [PATCH 6/6] config: reject parsing of files over INT_MAX Jeff King
2020-04-10 22:04   ` Junio C Hamano
2020-04-10 22:15     ` Jeff King
2020-04-13  0:47       ` Taylor Blau [this message]
2020-04-13 22:14         ` Junio C Hamano
2020-04-13  0:49 ` [PATCH 0/6] better handling of gigantic config files Taylor Blau
2020-04-13 17:20   ` Jeff King
2020-04-13 17:23     ` Taylor Blau

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