Re: Request for stable 4.14.x inclusion: net: don't call update_pmtu unconditionally

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, Apr 27, 2018 at 03:51:25PM +0200, Greg KH wrote:
> On Fri, Apr 27, 2018 at 02:20:07PM +0200, Thomas Deutschmann wrote:
> > On 2018-04-22 23:50, Thomas Deutschmann wrote:
> > > Hi,
> > > 
> > > please add
> > > 
> > >> From f15ca723c1ebe6c1a06bc95fda6b62cd87b44559 Mon Sep 17 00:00:00 2001
> > >> From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> > >> Date: Thu, 25 Jan 2018 19:03:03 +0100
> > >> Subject: net: don't call update_pmtu unconditionally
> > >>
> > >> Some dst_ops (e.g. md_dst_ops)) doesn't set this handler. It may result to:
> > >> "BUG: unable to handle kernel NULL pointer dereference at           (null)"
> > >>
> > >> Let's add a helper to check if update_pmtu is available before calling it.
> > >>
> > >> Fixes: 52a589d51f10 ("geneve: update skb dst pmtu on tx path")
> > >> Fixes: a93bf0ff4490 ("vxlan: update skb dst pmtu on tx path")
> > >> CC: Roman Kapl <code@rkapl.cz>
> > >> CC: Xin Long <lucien.xin@gmail.com>
> > >> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> > >> Signed-off-by: David S. Miller <davem@davemloft.net>
> > > 
> > > to 4.14.x.
> > > 
> > > This fixes NULL derefs caused by a93bf0ff4490 ("vxlan: update
> > > skb dst pmtu on tx path"), which was backported to 4.14.24.
> > 
> > *ping* - Not yet applied and not yet queued. Is there a problem with the
> > patch which prevents a cherry-pick for 4.14.x?
> 
> This looks like an "obvious" fix for me to pick up.

Well, it would be "obvious" if it actually applied to the 4.14.y tree :(

Thomas, did you try this patch out?  I can't apply it as-is, it will
need a backport.  Please work on that, and test it out, as I don't get
the impression that you did that here.

Then post the working backport and I'll be glad to consider it for
future 4.14.y releases.

thanks,

greg k-h