From: Junio C Hamano <gitster@pobox.com>
To: Michael Haggerty <mhagger@alum.mit.edu>
Cc: git@vger.kernel.org, "Mantas Mikulėnas" <grawity@gmail.com>
Subject: Re: [PATCH] do_one_ref(): save and restore value of current_ref
Date: Wed, 17 Jul 2013 21:03:23 -0700 [thread overview]
Message-ID: <7voba04ir8.fsf@alter.siamese.dyndns.org> (raw)
In-Reply-To: <1373901857-28431-1-git-send-email-mhagger@alum.mit.edu> (Michael Haggerty's message of "Mon, 15 Jul 2013 17:24:17 +0200")
Michael Haggerty <mhagger@alum.mit.edu> writes:
> If do_one_ref() is called recursively, then the inner call should not
> permanently overwrite the value stored in current_ref by the outer
> call. Aside from the tiny optimization loss, peel_ref() expects the
> value of current_ref not to change across a call to peel_entry(). But
> in the presence of replace references that assumption could be
> violated by a recursive call to do_one_ref:
>
> do_for_each_entry()
> do_one_ref()
> builtin/describe.c:get_name()
> peel_ref()
> peel_entry()
> peel_object ()
> deref_tag_noverify()
> parse_object()
> lookup_replace_object()
> do_lookup_replace_object()
> prepare_replace_object()
> do_for_each_ref()
> do_for_each_entry()
> do_for_each_entry_in_dir()
> do_one_ref()
>
> The inner call to do_one_ref() was unconditionally setting current_ref
> to NULL when it was done, causing peel_ref() to perform an invalid
> memory access.
>
> So change do_one_ref() to save the old value of current_ref before
> overwriting it, and restore the old value afterward rather than
> setting it to NULL.
>
> Reported by: Mantas Mikulėnas <grawity@gmail.com>
>
> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
> ---
Thanks.
s/Reported by:/Reported-by:/ and lose the extra blank line after it?
I wonder if we can have an easy reproduction recipe in our tests.
next prev parent reply other threads:[~2013-07-18 4:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-13 13:27 Segfault in `git describe` Mantas Mikulėnas
2013-07-15 13:03 ` Michael Haggerty
2013-07-15 13:31 ` Mantas Mikulėnas
2013-07-15 15:24 ` [PATCH] do_one_ref(): save and restore value of current_ref Michael Haggerty
2013-07-18 4:03 ` Junio C Hamano [this message]
2013-07-19 17:43 ` Michael Haggerty
2013-07-19 19:34 ` Junio C Hamano
2013-07-24 14:35 ` Michael Haggerty
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=7voba04ir8.fsf@alter.siamese.dyndns.org \
--to=gitster@pobox.com \
--cc=git@vger.kernel.org \
--cc=grawity@gmail.com \
--cc=mhagger@alum.mit.edu \
/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).