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: Fri, 23 Mar 2012 10:55:18 -0400 [thread overview]
Message-ID: <1332514519.2199.25.camel@falcor> (raw)
In-Reply-To: <20120322150945.GW6589@ZenIV.linux.org.uk>
On Thu, 2012-03-22 at 15:09 +0000, Al Viro wrote:
> On Thu, Mar 22, 2012 at 10:53:04AM -0400, Mimi Zohar wrote:
> > > 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.
>
> Don't do it, then? If you _must_ write to xattr on final fput, I'd suggest
> starting to figure out if xattr needs its protection to be ->i_mutex - it
> might make sense to introduce a separate mutex for xattr crap. Or not - I'm
> not familiar enough with the guts of xattr handling in individual filesystems
> to tell if that would work (e.g. if it would need unpleasant changes to
> ->setattr() instances)...
After looking into this, the individual filesystems do their own xattr
locking. The i_mutex, however, is currently required to access
inode->i_op->setxattr() (and the isec). In addition, IMA-appraisal
requires the i_mutex in order to calculate the file hash.
Calling ima_file_free() after the mmap_sem is released, as opposed to
queueing the __fput(), won't work, as the file needs to be open in order
to calculate the file hash.
Calling ima_file_free() before taking the mmap_sem, could work, but at
that point we don't have access to the file handle. Do you see any other
options?
thanks,
Mimi
next prev parent reply other threads:[~2012-03-23 14:55 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
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 [this message]
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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