From: Matthew Wilcox <matthew@wil.cx>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-fsdevel@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Stephen Smalley <sds@tycho.nsa.gov>,
Christoph Hellwig <hch@infradead.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Eric Paris <eparis@parisplace.org>, Theodore Ts'o <tytso@mit.edu>,
Dave Chinner <david@fromorbit.com>,
James Morris <james.l.morris@oracle.com>,
Paul Moore <paul@paul-moore.com>,
Andrew Morton <akpm@linux-foundation.org>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] vfs: Fix possible NULL pointer dereference in inode_permission()
Date: Thu, 9 Jan 2014 14:42:39 -0700 [thread overview]
Message-ID: <20140109214239.GD29910@parisc-linux.org> (raw)
In-Reply-To: <20140109162731.12500986@gandalf.local.home>
On Thu, Jan 09, 2014 at 04:27:31PM -0500, Steven Rostedt wrote:
> Note, the crash came from stressing the deletion and reading of debugfs
> files. I was not able to recreate this via normal files. But I'm not
> sure they are safe. It may just be that the race window is much harder
> to hit.
But "normal" files have a 'destroy_inode' method. So you've basically
only fixed it for debugfs (and maybe a few other unusual filesystems).
Why doesn't the code look like this:
static void i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
__destroy_inode(inode);
if (inode->i_sb->s_op->destroy_inode)
inode->i_sb->s_op->destroy_inode(inode);
else
kmem_cache_free(inode_cachep, inode);
}
static void destroy_inode(struct inode *inode)
{
BUG_ON(!list_empty(&inode->i_lru));
call_rcu(&inode->i_rcu, i_callback);
}
We'd then have to get rid of all the call_rcu() invocations in individual
filesystems' destroy_inode methods, but that doesn't sound like a bad
thing to me.
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
next prev parent reply other threads:[~2014-01-09 21:42 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-09 21:27 [PATCH] vfs: Fix possible NULL pointer dereference in inode_permission() Steven Rostedt
2014-01-09 21:42 ` Matthew Wilcox [this message]
2014-01-09 21:50 ` Steven Rostedt
2014-01-09 22:31 ` Al Viro
[not found] ` <CA+55aFzCTPYEQCPnLBi1CwmMTocVqCFiCuJ391HkVx1CMw61ug@mail.gmail.com>
2014-01-09 23:10 ` Paul E. McKenney
2014-01-09 23:25 ` Steven Rostedt
2014-01-09 23:27 ` Steven Rostedt
2014-01-09 23:37 ` Eric Paris
2014-01-09 23:45 ` Steven Rostedt
2014-01-09 23:53 ` Linus Torvalds
2014-01-10 0:06 ` Al Viro
2014-01-10 0:09 ` Al Viro
2014-01-10 0:18 ` Linus Torvalds
2014-01-10 2:36 ` James Morris
2014-01-10 9:31 ` Christoph Hellwig
2014-01-10 18:14 ` Ben Myers
2014-01-11 10:32 ` Christoph Hellwig
2014-01-09 23:45 ` Paul E. McKenney
2014-01-09 23:59 ` Steven Rostedt
2014-01-10 0:44 ` Paul E. McKenney
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