linux-kernel - Re: [PATCH] apply: refuse touching a file beyond symlink

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Message-ID: <20150130204805.GA10616@peff.net>
Date:	Fri, 30 Jan 2015 15:48:05 -0500
From:	Jeff King <peff@...f.net>
To:	Junio C Hamano <gitster@...ox.com>
Cc:	Git Mailing List <git@...r.kernel.org>,
	Josh Boyer <jwboyer@...oraproject.org>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	twaugh@...hat.com, Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] apply: refuse touching a file beyond symlink

On Fri, Jan 30, 2015 at 12:20:02PM -0800, Junio C Hamano wrote:

> Jeff King <peff@...f.net> writes:
> 
> > I had the impression that we did not apply in any arbitrary order that
> > could work, but rather that we did deletions first followed by
> > additions. But I am fairly ignorant of the apply code.
> 
> No, you are thinking about the write-out of the finished result,
> which may have to turn existing directory to a file or vice versa on
> the filesystem, but that happens _after_ we decide what to turn into
> what else, completely in-core.
> 
> And the decision to determine what the input _means_ should not
> depend on the order of patches in the input.

Ah, OK. Yeah, doing it progressively can only be accurate if our
name-checks follow the same order as applying, because we are checking
against a particular state.

But could we instead pull this check to just before the write-out time?
That is, to let any horrible thing happen in-core, as long as what we
write out to the index and the filesystem is sane?

-Peff
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