Re: [PATCH 4.4.y] tcp: Fix missing range_truesize enlargement in the backport

Greg Kroah-Hartman
2018-08-16T15:16:57Z

On Wed, Aug 15, 2018 at 10:02:30PM +0200, Michal Kubecek wrote:
> On Wed, Aug 15, 2018 at 01:11:21PM +0200, Greg Kroah-Hartman wrote:
> > On Wed, Aug 15, 2018 at 11:58:46AM +0200, Takashi Iwai wrote:
> > > The 4.4.y stable backport dc6ae4dffd65 for the upstream commit
> > > 3d4bf93ac120 ("tcp: detect malicious patterns in
> > > tcp_collapse_ofo_queue()") missed a line that enlarges the
> > > range_truesize value, which broke the whole check.
> > >
> > > Fixes: dc6ae4dffd65 ("tcp: detect malicious patterns in tcp_collapse_ofo_queue()")
> > > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > > ---
> > >
> > > Greg, this is a fix-up specific to 4.4.y stable backport that had a
> > > slightly different form from upstream fix. I haven't looked at the
> > > older trees, but 4.9.y and later took the upstream fix as is, so this
> > > patch isn't needed for them.
> > >
> > > The patch hasn't been tested with the real test case, though; let me
> > > know if the current code is intended. Thanks!
> >
> > Hm, I did the initial backport, and then Eric showed what I got wrong
> > and fixed that up, so being still wrong is not inconceivable at all :)
>
> Takashi's follow-up patch is what makes the backport work the same way
> as the original mainline commit 3d4bf93ac120. Without it, range_truesize
> will be always equal to truesize of first packet in a contiguous range
> so that the condition
>
> range_truesize != head->truesize
>
> will be always false (and there would be no point having range_truesize
> variable at all).

Thanks, I've now queued this up.

greg k-h