From: ori@eigenstate.org
To: ori@eigenstate.org, git@vger.kernel.org
Subject: Re: [PATCH] Avoid infinite loop in malformed packfiles
Date: Sat, 22 Aug 2020 19:52:35 -0700 [thread overview]
Message-ID: <5374D56FBAB7F3BCD976B433934DEFCA@eigenstate.org> (raw)
In-Reply-To: <20200823005236.10386-1-ori@eigenstate.org>
> In packfile.c:1680, there's an infinite loop that tries to get
> to the base of a packfile. With offset deltas, the offset needs
> to be greater than 0, so it's always walking backwards, and the
> search is guaranteed to terminate.
>
> With reference deltas, there's no check for a cycle in the
> references, so a cyclic reference will cause git to loop
> infinitely, growing the delta_stack infinitely, which will
> cause it to consume all available memory as as a full CPU
> core.
>
> This change puts an arbitrary limit of 10,000 on the number
> of iterations we make when chasing down a base commit, to
> prevent looping forever, using all available memory growing
> the delta stack.
For context, I discovered this accidentally when I
introduced a bug in pack deltification in git9 (my
implementation of git for plan 9). An example of a
packfile and index that will reproduce this issue
is available here:
https://eigenstate.org/tmp/95a0f4f3f3f21d723d501552eaf22ff4055e13a4.pack
https://eigenstate.org/tmp/95a0f4f3f3f21d723d501552eaf22ff4055e13a4.idx
The suggestion to just cap the depth instead of
doing full cycle detection came from Jeff King
(peff@peff.net)
next prev parent reply other threads:[~2020-08-23 2:52 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-23 0:52 [PATCH] Avoid infinite loop in malformed packfiles Ori Bernstein
2020-08-23 2:52 ` ori [this message]
2020-08-23 3:08 ` Eric Sunshine
2020-08-23 3:11 ` Ori Bernstein
2020-08-23 6:26 ` René Scharfe
2020-08-23 20:41 ` Ori Bernstein
2020-08-24 16:06 ` René Scharfe
2020-08-24 20:12 ` Jeff King
2020-08-24 20:38 ` Junio C Hamano
2020-08-24 20:52 ` Jeff King
2020-08-24 21:22 ` Junio C Hamano
2020-08-30 3:33 ` ori
2020-08-30 10:56 ` René Scharfe
2020-08-30 16:15 ` Junio C Hamano
2020-08-31 9:29 ` Jeff King
2020-08-31 16:32 ` Junio C Hamano
2020-08-31 19:23 ` Jeff King
2020-08-31 16:50 ` ori
2020-08-24 17:33 ` Junio C Hamano
2020-08-24 20:30 ` Junio C Hamano
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5374D56FBAB7F3BCD976B433934DEFCA@eigenstate.org \
--to=ori@eigenstate.org \
--cc=git@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).