linux-kernel - Re: [PATCH] aio: fix a user triggered use after free (and fix freeze protection of aio writes)

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Date:   Sat, 29 Oct 2016 13:09:25 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Christoph Hellwig <hch@....de>, Jan Kara <jack@...e.cz>,
        Dmitry Monakhov <dmonakhov@...nvz.org>,
        Jeff Moyer <jmoyer@...hat.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-aio@...ck.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] aio: fix a user triggered use after free (and fix freeze
 protection of aio writes)

On Sat, Oct 29, 2016 at 12:17 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
>
> AFAICS, the possibility of dropping the last reference to struct file
> before ->write_iter() has returned is fundamentally broken.  I might be
> missing something subtle here, but...

Ok, let's add a get_file(); fput(); around that whole iter call sequence.

And that's a separate issue from "we should hold the fs freezer lock
around the whole operation". So I think we need both.

Does that make everybody happy?

              Linus