Re: [PATCH 4/7] conf, tcp, udp: Arrays for ports need 2^16 values, not 2^16-8

[Stefano Brivio <sbrivio@redhat.com>]

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On Thu, 22 Sep 2022 16:43:24 +1000
David Gibson <david(a)gibson.dropbear.id.au> wrote:

> On Wed, Sep 21, 2022 at 10:55:04PM +0200, Stefano Brivio wrote:
> > Reported by David but also by Coverity (CWE-119):
> > 
> > 	In conf_ports: Out-of-bounds access to a buffer
> > 
> > ...not in practice, because the allocation size is rounded up
> > anyway, but not nice either.  
> 
> So... this helps, but it's not enough.  For starters, this is still
> conceptually wrong - there should be 65536 bits in the bitmap, not
> 65535 (USHRT_MAX).  This patch just masks it by rounding up to 65536
> rather than down to 65528.

Ah, yes, I indeed wanted to have 65536 values in the bitmap (see commit
title), and this does it, but there's no reason to make it implicit.

> Alas, this is not the only buffer overrun caused by an off-by-one in
> port numbers: the delta_to_tap etc. global arrays in tcp.c and udp.c
> should also have length 65536, rather than USHRT_MAX.  So should
> tcp_sock_init_lo and friends.  There are also similar problems in
> icmp.c with echo request id rather than port number.
> 
> Not a buffer overrun, but the USHRT_MAX in udp_remap_to_tap() and
> udp_remap_to_init() is also out by one (consider the case of
> delta==0).
> 
> I have a series which makes a number of cleanups to the port mapping
> handling.  It fixes this bug and adds typing stuff that should make it
> harder to make similar mistakes in future.
> 
> I held off on sending, since it's currently based on a lot of my
> outstanding patches.  I think it wouldn't be too hard to rebase
> directly on master, should I do that so you can fix this before going
> on to debug the rest of my outstanding stuff?

If it's not too much effort for you, yes, that would be appreciated.

I hope to be able to push out everything else later today, it's just
one glitch still occurring in test_iperf3() -- sometimes, clients and
servers terminate properly, but we don't see it for some reason.

-- 
Stefano