linux-kernel - Re: [git pull] gadgetfs fixes

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Message-ID: <20150315013948.GU29656@ZenIV.linux.org.uk>
Date:	Sun, 15 Mar 2015 01:39:49 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Alexander Holler <holler@...oftware.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-usb@...r.kernel.org
Subject: Re: [git pull] gadgetfs fixes

On Sun, Mar 15, 2015 at 01:39:21AM +0100, Alexander Holler wrote:
> Am 13.03.2015 um 17:42 schrieb Al Viro:
> > 	Assorted fixes around AIO on gadgetfs: leaks, use-after-free,
> > troubles caused by ->f_op flipping.  Please, pull from
> > git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git gadget
> > 
> > Shortlog:
> > Al Viro (8):
> >       new helper: dup_iter()
> >       move iov_iter.c from mm/ to lib/
> >       gadget/function/f_fs.c: close leaks
> >       gadget/function/f_fs.c: use put iov_iter into io_data
> >       gadget/function/f_fs.c: switch to ->{read,write}_iter()
> 
> >       gadgetfs: use-after-free in ->aio_read()
> 
> If that patch ends up in the stable kernels (as it is marked as such),
> it needs a
> 	value = -ENOMEM
> before that added "goto fail;", otherwise the return value is unitialized.

Umm...  If I'm not misparsing what you said, you are talking about the
one that gets removed by
-       if (iv) {
-               priv->iv = kmemdup(iv, nr_segs * sizeof(struct iovec),
-                                  GFP_KERNEL);
-               if (!priv->iv) {
-                       kfree(priv);
-                       goto fail;
-               }
-       }
in "gadget: switch ep_io_operations to ->read_iter/->write_iter" very
shortly afterwards, and _that_ is a prereq for ->f_op flipping fixes,
which is also clear -stable fodder.  But yes, it's a bisect hazard and
a cherry-pick one as well.  Nice catch...
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