Re: [PATCH RFC] tun: remove of user-controlled memory allocation

[David Miller]

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Date: Mon, 1 Nov 2010 10:27:49 +0200

> Untested, this is just an RFC.
> 
> tun does a kmalloc where userspace controls the length. This will
> produce warnings in kernel log when the length is too large, or might
> block for a long while. A simple fix is to avoid the allocatiuon
> altogether, and copy from user in a loop.
> 
> However, with this patch an illegal address passed to the ioctl might
> leave the filter disabled.  Is this something we care about?  If
> yes we could recover by creating a copy of the filter.  Thoughts?
> 
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

I think the key issue in situations like this is simply to make
sure that reasonable things that worked before, still do afterwards.

And I think your patch does that, so it's fine as far as I can tell.
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