linux-kernel - Re: [PATCH] locks: use file

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Date:	Fri, 1 Jul 2016 09:47:05 -0400
From:	"J. Bruce Fields" <bfields@...ldses.org>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	Miklos Szeredi <mszeredi@...hat.com>,
	Al Viro <viro@...IV.linux.org.uk>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-unionfs@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] locks: use file_inode()

On Fri, Jul 01, 2016 at 09:05:10AM -0400, Jeff Layton wrote:
> On Fri, 2016-07-01 at 14:56 +0200, Miklos Szeredi wrote:
> > (Another one for the f_path debacle.)
> > 
> > ltp fcntl33 testcase caused an Oops in selinux_file_send_sigiotask.
> > 
> > The reason is that generic_add_lease() used filp->f_path.dentry->inode
> > while all the others use file_inode().  This makes a difference for files
> > opened on overlayfs since the former will point to the overlay inode the
> > latter to the underlying inode.
> > 
> > So generic_add_lease() added the lease to the overlay inode and
> > generic_delete_lease() removed it from the underlying inode.  When the file
> > was released the lease remained on the overlay inode's lock list, resulting
> > in use after free.
> > 
> > Reported-by: Eryu Guan <eguan@...hat.com>
> > Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
> > Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
> > Cc: <stable@...r.kernel.org>
> > Cc: Jeff Layton <jlayton@...chiereds.net>
> > Cc: "J. Bruce Fields" <bfields@...ldses.org>
> > ---
> >  fs/locks.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/locks.c b/fs/locks.c
> > index 7c5f91be9b65..ee1b15f6fc13 100644
> > --- a/fs/locks.c
> > +++ b/fs/locks.c
> > @@ -1628,7 +1628,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
> >  {
> >  	struct file_lock *fl, *my_fl = NULL, *lease;
> >  	struct dentry *dentry = filp->f_path.dentry;
> > -	struct inode *inode = dentry->d_inode;
> > +	struct inode *inode = file_inode(filp);
> >  	struct file_lock_context *ctx;
> >  	bool is_deleg = (*flp)->fl_flags & FL_DELEG;
> >  	int error;
> 
> Looks good. Al or Bruce, if either of you have remaining patches this
> cycle then could one of you take this one? Otherwise, I can queue up a
> branch with it.
> 
> Reviewed-by: Jeff Layton <jlayton@...hat.com>

I'll take it and pass it along in a pull request later today, unless
somebody tells me otherwise.

--b.