linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Miklos Szeredi <miklos@szeredi.hu>
To: trond.myklebust@fys.uio.no
Cc: chrisw@sous-sol.org, matthew@wil.cx,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: DoS with POSIX file locks?
Date: Wed, 22 Mar 2006 21:19:40 +0100	[thread overview]
Message-ID: <E1FM9nw-00029f-00@dorka.pomaz.szeredi.hu> (raw)
In-Reply-To: <1143058078.8929.21.camel@lade.trondhjem.org> (message from Trond Myklebust on Wed, 22 Mar 2006 15:07:57 -0500)

> You'd have to ensure that none of the threads involved are able to grab
> new posix locks in the period between the unsharing of current->files to
> the moment when current->files->owner is swapped.
> 
> If not, one thread could in theory open a new file and grab a lock that
> can never be unlocked because its lockowner gets stolen away from it by
> another execing thread.

This race is already there.  Header comment on steal_locks() documents
it.

The patch does open this race window much wider, because pending locks
are also transfered to the task doing the exec.  The original
steal_locks() only stole already held locks.  But I don't think this
fundamentaly changes things.  It just shows more clearly how ugly the
current semantics are.

Miklos

      reply	other threads:[~2006-03-22 20:20 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-03-20 11:41 DoS with POSIX file locks? Miklos Szeredi
2006-03-20 12:11 ` Matthew Wilcox
2006-03-20 12:19   ` Miklos Szeredi
2006-03-20 12:39     ` Matthew Wilcox
2006-03-20 12:52       ` Miklos Szeredi
2006-03-20 13:13         ` Arjan van de Ven
2006-03-20 13:24           ` Miklos Szeredi
2006-03-20 13:30             ` Arjan van de Ven
2006-03-20 13:39               ` Miklos Szeredi
2006-03-20 15:32         ` Matthew Wilcox
2006-03-20 16:41           ` Miklos Szeredi
2006-03-20 20:35             ` J. Bruce Fields
2006-03-21  6:38               ` Miklos Szeredi
2006-03-20 18:22           ` Trond Myklebust
2006-03-21  9:44             ` Miklos Szeredi
2006-03-21 17:28               ` Trond Myklebust
2006-03-21 17:58                 ` Miklos Szeredi
2006-03-21 18:16                   ` Trond Myklebust
2006-03-21 19:16                   ` Chris Wright
2006-03-22  6:21                     ` Miklos Szeredi
2006-03-22 11:12                       ` Trond Myklebust
2006-03-22 12:16                         ` Miklos Szeredi
2006-03-22 15:56                           ` Trond Myklebust
2006-03-22 16:34                             ` Miklos Szeredi
2006-03-22 20:07                               ` Trond Myklebust
2006-03-22 20:19                                 ` Miklos Szeredi [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=E1FM9nw-00029f-00@dorka.pomaz.szeredi.hu \
    --to=miklos@szeredi.hu \
    --cc=chrisw@sous-sol.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=matthew@wil.cx \
    --cc=trond.myklebust@fys.uio.no \
    /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).