From: erik quanstrom <quanstro@quanstro.net>
To: 9fans@9fans.net
Subject: Re: [9fans] Race condition in /sys/src/9/pc/trap.c?
Date: Thu, 30 Jul 2009 10:39:08 -0400 [thread overview]
Message-ID: <ba55ec1b6091a6115fc5f3d8a34b7c8a@quanstro.net> (raw)
In-Reply-To: <Pine.LNX.4.64-044.0907301023450.5490@unix10.andrew.cmu.edu>
> > plan 9 threads are cooperatively scheduled. so
> > the correct term is proc. but you are correct,
> > another proc sharing memory with this one
> > could be running. however, that proc would
> > not have access to this proc's stack. (rfork
> > doesn't allow shared stack.) and even if it
> > did, plan 9 stacks don't shrink.
>
> What if sp points inside a segment which is not the actual stack segment?
> Then could someone else come along and segdetach() it in between the two
> mentioned lines?
see below:
> > let's suppose that the address is invalid later.
> > the kernel always moves data to/from user
> > buffers outside of any locks because even
> > valid targets may be paged out. if the address
> > is truely invalid, waserror() will be true and
> > the else branch starting at 714 will be executed
if you think this is possible, why don't you build a
test case and prove that it can happen. the easiest
way would be to disable the check completely.
- erik
prev parent reply other threads:[~2009-07-30 14:39 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-07-30 4:03 Matthew J Jones
2009-07-30 11:27 ` erik quanstrom
2009-07-30 14:25 ` Elizabeth Jones
2009-07-30 14:37 ` Sape Mullender
2009-07-30 15:01 ` cinap_lenrek
2009-07-30 15:24 ` cinap_lenrek
2009-07-30 15:17 ` cinap_lenrek
2009-07-30 15:54 ` Charles Forsyth
2009-07-31 13:07 ` Charles Forsyth
2009-07-31 13:28 ` Richard Miller
2009-07-31 17:13 ` cinap_lenrek
2009-07-31 18:00 ` erik quanstrom
2009-07-31 18:08 ` Devon H. O'Dell
2009-07-31 18:18 ` erik quanstrom
2009-07-31 18:35 ` Devon H. O'Dell
2009-07-31 21:52 ` cinap_lenrek
2009-07-31 19:31 ` Charles Forsyth
2009-07-31 19:40 ` erik quanstrom
2009-07-31 20:41 ` Charles Forsyth
2009-07-30 15:20 ` erik quanstrom
2009-07-30 14:39 ` erik quanstrom [this message]
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
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ba55ec1b6091a6115fc5f3d8a34b7c8a@quanstro.net \
--to=quanstro@quanstro.net \
--cc=9fans@9fans.net \
/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.
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 NNTP newsgroup(s).