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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>
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 14:22:12 +0000	[thread overview]
Message-ID: <20120322142212.GV6589@ZenIV.linux.org.uk> (raw)
In-Reply-To: <1332356057-3356-11-git-send-email-zohar@linux.vnet.ibm.com>

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.

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.

  parent reply	other threads:[~2012-03-22 14:22 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 [this message]
2012-03-22 14:53     ` Mimi Zohar
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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