From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
David Safford <safford@linux.vnet.ibm.com>,
Dmitry Kasatkin <dmitry.kasatkin@intel.com>,
Matt Helsley <matt.helsley@gmail.com>,
Mimi Zohar <zohar@us.ibm.com>
Subject: Re: [PATCH v3 10/12] ima: defer calling __fput()
Date: Thu, 22 Mar 2012 10:53:04 -0400 [thread overview]
Message-ID: <1332427986.2218.53.camel@falcor> (raw)
In-Reply-To: <20120322142212.GV6589@ZenIV.linux.org.uk>
On Thu, 2012-03-22 at 14:22 +0000, Al Viro wrote:
> On Wed, Mar 21, 2012 at 02:54:15PM -0400, Mimi Zohar wrote:
> > If a file is closed before it is munmapped, __fput() is called with
> > the mmap_sem taken. With IMA-appraisal enabled, this results in an
> > mmap_sem/i_mutex lockdep. ima_defer_fput() increments the f_count
> > to defer __fput() being called until after the mmap_sem is released.
>
> NAK. It's far too heavy-weight for what's a very common path. Worse,
> it causes different locking conditions on IMA and non-IMA kernels and makes
> bugs harder to spot. Rejected with extreme prejudice; please, fix your
> locking instead.
Al, thanks for replying! I realize you are very prejudiced against IMA,
but have you taken a look at IMA-appraisal? It probably would have been
better if we used another name in order to avoid this prejudice, but
unfortunately we didn't. :( IMA-appraisal is about enforcing file
integrity.
> BTW, you've missed several other places in mm/* doing fput(), so it wouldn't
> be enough to paper over your problem anyway.
>
> Final fput() *can* happen under mmap_sem. Period.
I think I got that loud and clear; otherwise we wouldn't have come up
with deferring the __fput(). We have a very real problem here - writing
extended attributes requires taking the i_mutex. I'm open to any
suggestions.
thanks,
Mimi
next prev parent reply other threads:[~2012-03-22 14:53 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-21 18:54 [PATCH v3 00/12] ima: appraisal extension Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 01/12] vfs: extend vfs_removexattr locking Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 02/12] vfs: move ima_file_free before releasing the file Mimi Zohar
2012-03-22 14:23 ` Kasatkin, Dmitry
2012-03-21 18:54 ` [PATCH v3 03/12] ima: free securityfs violations file Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 04/12] ima: integrity appraisal extension Mimi Zohar
2012-03-22 14:28 ` Kasatkin, Dmitry
2012-03-21 18:54 ` [PATCH v3 05/12] ima: add appraise action keywords and default rules Mimi Zohar
2012-03-22 14:27 ` Kasatkin, Dmitry
2012-03-21 18:54 ` [PATCH v3 06/12] ima: allocating iint improvements Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 07/12] ima: replace iint spinlock with rwlock/read_lock Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 08/12] ima: add inode_post_setattr call Mimi Zohar
2012-03-22 14:21 ` Kasatkin, Dmitry
2012-03-21 18:54 ` [PATCH v3 09/12] ima: add ima_inode_setxattr/removexattr function and calls Mimi Zohar
2012-03-22 14:22 ` Kasatkin, Dmitry
2012-03-21 18:54 ` [PATCH v3 10/12] ima: defer calling __fput() Mimi Zohar
2012-03-22 14:07 ` Kasatkin, Dmitry
2012-03-22 14:22 ` Al Viro
2012-03-22 14:53 ` Mimi Zohar [this message]
2012-03-22 14:58 ` Kasatkin, Dmitry
2012-03-22 15:09 ` Al Viro
2012-03-22 15:19 ` Kasatkin, Dmitry
2012-03-22 15:39 ` Al Viro
2012-03-23 14:55 ` Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 11/12] ima: add support for different security.ima data types Mimi Zohar
2012-03-21 18:54 ` [PATCH v3 12/12] ima: digital signature verification support Mimi Zohar
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