linux-kernel - Re: [patch] nfs: fix locking in nfs/inode.c in nfs_free_open

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:	Thu, 26 Jul 2007 13:23:37 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Trond Myklebust <trond.myklebust@....uio.no>
Cc:	Christian Krafft <krafft@...ibm.com>, linux-kernel@...r.kernel.org
Subject: Re: [patch] nfs: fix locking in nfs/inode.c in nfs_free_open_context

On Wednesday 25 July 2007, Trond Myklebust wrote:
> 
> On Wed, 2007-07-25 at 17:08 +0200, Christian Krafft wrote:
> 
> > Obviously the locking code in nfs_free_open_context is wrong.
> > Checking the list for entries and removing the entry should be an atomic operation.
> 
> Wrong. It is quite safe to test the structure member ctx->list for
> emptiness outside the spinlock because we have an explicit guarantee
> that nobody else has a reference to this structure, plus the
> atomic_dec_and_test() in kref_put() has acted as a memory barrier for
> us.

Well, the real question then is how the ctx can still be present in the
nfsi->open_files list. Since we are in nfs_free_open_context(), there
must not be any pointer to the ctx anywhere, but still we have this other
thread calling get_nfs_open_context() on it.

	Arnd <><
-
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/