linux-kernel - Re: [PATCH 0/3] Fixes for vfs-scale and vfs-automount

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 24 Feb 2011 14:59:47 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Ian Kent <raven@...maw.net>
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>,
	David Howells <dhowells@...hat.com>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
	npiggin@...il.com
Subject: Re: [PATCH 0/3] Fixes for vfs-scale and vfs-automount

On Thu, Feb 24, 2011 at 06:07:33PM +0800, Ian Kent wrote:
> > I really don't like the look of autofs4_tree_busy(), BTW - you don't need
> > RCU to get races here; just a plain chdir("../../.."); done by a process
> > that sits deep enough in subtree you are checking can very well race with
> > your check, so that your iterator gets through the new cwd before chdir()
> > and through the old one after it...
> 
> Yes, that's a problem.
> 
> Previously the dcache_lock would have blocked on the dput() ... mmm, I'd
> missed that so far, although Nick didn't talk with me about his changes
> very much at all and I didn't pay enough attention to his patch series
> along the way, oops!

Well...  In principle, you could mark all mountpoints in a tree as managed,
have an "expiry search in progress" flag to stop everything in there while
the expiry happens, then wait out all RCU walks in progress, then go ahead
with your expiry checks.  Would that work for you?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/