lkml.org 
[lkml]   [2016]   [Oct]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] aio: fix a user triggered use after free (and fix freeze protection of aio writes)
On Sat, Oct 29, 2016 at 11:52 AM, Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> And that call can happen as soon as we return from __blockdev_direct_IO()
> (even earlier, actually). As soon as that happens, the reference to
> struct file we'd acquired in io_submit_one() is dropped. If descriptor
> table had been shared, another thread might have already closed that sucker,
> and fput() from aio_complete() would free struct file.

But that's the point. We don't *do* anything like that any more. We
now always do the final access from aio_complete(). So it doesn't
matter if that is called asynchronously (very early) or not.

That's the whole point of the patch. Exactly to do everything either
*before* we even submit it (at which point no completion can happen),
or doing it in aio_complete() which is guaranteed to be after the
submission. No races, no use-after-free.

What am I missing?

Linus

\
 
 \ /
  Last update: 2016-10-29 21:08    [W:2.086 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site