From: Duy Nguyen <pclouds@gmail.com>
To: Jeff King <peff@peff.net>
Cc: steve.norman@thomsonreuters.com, Git Mailing List <git@vger.kernel.org>
Subject: Re: Troubleshoot clone issue to NFS.
Date: Sun, 24 May 2015 16:00:36 +0700 [thread overview]
Message-ID: <CACsJy8Bb1O7QZtiPWdzYwYgOdV0dLDgD3Xu_YaWNUbsuTqJB5g@mail.gmail.com> (raw)
In-Reply-To: <20150522071224.GA10734@peff.net>
On Fri, May 22, 2015 at 2:12 PM, Jeff King <peff@peff.net> wrote:
> So I think there are two possibilities for improving this:
>
> 1. Find places where we expect the object will not exist (like the
> collision_test check you pointed out) and use a
> "has_sha1_file_fast" that accepts that it may very occasionally
> erroneously return false. In this case it would mean potentially
> skipping a collision check, but I think that is OK. That could have
> security implications, but only if an attacker:
>
> a. has broken sha1 to generate a colliding object
>
> b. can manipulate the victim into repacking in a loop
>
> c. can manipulate the victim into fetching (or receiving a push)
> simultaneously with (b)
>
> at which point they can try to race the repack procedure to add
> their colliding object to the repository. It seems rather unlikely
> (especially part a).
In case you want to back away from option 2 because it starts to leak
raciness, which your old commit tried to fix in the first place. I
think the only other place that tests for lots of non-existent loose
objects is write_sha1_file (e.g. "tar -xf bigtarball.tar.gz; cd
bigtarball; git init; git add ."). But the number of calls should be
much smaller compared to index-pack and it does not use has_sha1_file,
it uses check_and_freshen_file() instead.
There are other places where has_sha1_file() may return 0, but I think
the number of calls is even smaller to bother (shallow.c,
fetch-pack.c, apply.c, buik-checkin.c)
--
Duy
next prev parent reply other threads:[~2015-05-24 9:01 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-21 13:13 Troubleshoot clone issue to NFS steve.norman
2015-05-21 14:00 ` Christian Couder
2015-05-21 14:31 ` Duy Nguyen
2015-05-21 14:38 ` Duy Nguyen
2015-05-21 15:53 ` steve.norman
2015-05-22 0:16 ` Duy Nguyen
2015-05-22 7:12 ` Jeff King
2015-05-22 8:35 ` steve.norman
2015-05-22 10:05 ` Duy Nguyen
2015-05-22 14:37 ` Junio C Hamano
2015-05-22 15:02 ` steve.norman
2015-05-22 23:51 ` [PATCH/RFC 0/3] using stat() to avoid re-scanning pack dir Jeff King
2015-05-22 23:51 ` [PATCH 1/3] stat_validity: handle non-regular files Jeff King
2015-05-23 11:00 ` Michael Haggerty
2015-05-24 8:29 ` Jeff King
2015-05-22 23:52 ` [PATCH 2/3] cache.h: move stat_validity definition up Jeff King
2015-05-22 23:54 ` [PATCH 3/3] prepare_packed_git: use stat_validity to avoid re-reading packs Jeff King
2015-05-23 1:19 ` [PATCH/RFC 0/3] using stat() to avoid re-scanning pack dir Duy Nguyen
2015-05-23 1:21 ` Duy Nguyen
2015-05-24 8:20 ` Jeff King
2015-05-24 9:00 ` Duy Nguyen [this message]
2015-06-05 12:01 ` Troubleshoot clone issue to NFS steve.norman
2015-06-05 12:18 ` Jeff King
2015-06-05 12:29 ` [PATCH] index-pack: avoid excessive re-reading of pack directory Jeff King
2015-06-09 17:24 ` Jeff King
2015-06-09 17:41 ` Jeff King
2015-06-10 3:46 ` Shawn Pearce
2015-06-10 14:00 ` Jeff King
2015-06-10 14:36 ` Duy Nguyen
2015-06-10 21:34 ` Shawn Pearce
2015-06-05 14:20 ` Troubleshoot clone issue to NFS steve.norman
2015-06-16 20:50 ` Jeff King
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