From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-fsdevel@vger.kernel.org, hch@infradead.org,
warthog9@kernel.org, david@fromorbit.com, jmorris@namei.org,
kyle@mcmartin.ca, hpa@zytor.com, akpm@linux-foundation.org,
torvalds@linux-foundation.org, mingo@elte.hu, eparis@redhat.com,
viro@zeniv.linux.org.uk, Matthew Wilcox <matthew@wil.cx>
Subject: Re: [PATCH 0/4] IMA: making i_readcount a first class inode citizen
Date: Sat, 06 Nov 2010 20:03:39 -0400 [thread overview]
Message-ID: <1289088219.3268.4.camel@localhost.localdomain> (raw)
In-Reply-To: <20101105190827.GC6492@fieldses.org>
On Fri, 2010-11-05 at 15:08 -0400, J. Bruce Fields wrote:
> On Fri, Nov 05, 2010 at 01:38:05PM -0400, Mimi Zohar wrote:
> > On Fri, 2010-11-05 at 12:28 -0400, J. Bruce Fields wrote:
> > > On Fri, Nov 05, 2010 at 07:08:06AM -0400, Mimi Zohar wrote:
> >
> > > > Right, like the ima_file_check(), which is after the __dentry_open().
> > > > Al, is it possible to move the break_lease() in may_open() to later?
> > >
> > > That would still leave a race like:
> > >
> > > check count
> > > bump count
> > > break lease
> > > set lease
> > >
> > > But we could extend the i_lock to prevent the lease being bumped between
> > > the two steps on the right-hand side.
> >
> > The latest i_readcount patchset, i_readcount is atomic and doesn't
> > require i_lock, at least for IMA. Have to think about this more ....
> >
> > > At that point I think we'd be done? We're assured the count is still
> > > zero while the lease is added to the inode, so anyone in the process of
> > > doing an open has yet to reach the break_lease, which will see the newly
> > > added lease.
> > >
> > > That leaves the problem that leases really should be broken on anything
> > > that changes the attributes or the dentries pointing to the inode:
> > > setattr, link, unlink, rename, at least.
> >
> > For this reason, IMA is now taking i_mutex, preventing file metadata
> > from changing.
>
> Lease code could do that as well. (Probably just with a trylock,
> failing the setlease if we can't get the lock.)
>
> That misses rename, though, which doesn't take the i_mutex on the
> renamed file. Which makes sense.
fs/namei.c: vfs_rename_other() seems to be taking the i_mutex. Am I
looking in the wrong place?
> But a lease is used to give file server clients the right to do an open
> locally, and we want them to be able to guarantee to applications that
> the path (well, the last component, at least) still refers to the same
> file at open time.
Mimi
next prev parent reply other threads:[~2010-11-07 0:03 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-28 22:02 [PATCH 0/4] IMA: making i_readcount a first class inode citizen Mimi Zohar
2010-10-28 22:02 ` [PATCH 1/4] IMA: define readcount functions Mimi Zohar
2010-10-28 22:02 ` [PATCH 2/4] IMA: maintain i_readcount in the VFS layer Mimi Zohar
2010-10-29 14:13 ` Valdis.Kletnieks
2010-10-29 15:15 ` Valdis.Kletnieks
2010-10-28 22:02 ` [PATCH 3/4] IMA: remove IMA imbalance checking Mimi Zohar
2010-10-28 22:02 ` [PATCH 4/4] IMA: making i_readcount a first class inode citizen Mimi Zohar
2010-10-28 22:24 ` [PATCH 0/4] " Dave Chinner
2010-10-28 22:29 ` Linus Torvalds
2010-10-28 22:38 ` Mimi Zohar
2010-10-28 22:46 ` Linus Torvalds
2010-10-28 23:25 ` Al Viro
2010-10-28 22:45 ` Eric Paris
2010-10-29 0:30 ` Mimi Zohar
2010-11-06 10:44 ` Pavel Machek
2010-11-05 1:12 ` J. Bruce Fields
2010-11-05 11:08 ` Mimi Zohar
2010-11-05 16:28 ` J. Bruce Fields
2010-11-05 17:38 ` Mimi Zohar
2010-11-05 19:08 ` J. Bruce Fields
2010-11-05 20:58 ` J. Bruce Fields
2010-11-07 0:03 ` Mimi Zohar [this message]
-- strict thread matches above, loose matches on Subject: below --
2011-02-14 20:29 Mimi Zohar
2011-02-16 23:08 ` Mimi Zohar
2011-02-17 1:46 ` James Morris
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