Re: [PATCH] locks: use file_inode()

[Jeff Layton <jlayton@redhat.com>]

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@redhat.com>
> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
> Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
> Cc: <stable@vger.kernel.org>
> Cc: Jeff Layton <jlayton@poochiereds.net>
> Cc: "J. Bruce Fields" <bfields@fieldses.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@redhat.com>