From: Bernd Edlinger <bernd.edlinger@hotmail.de>
To: "Lambrecht Jürgen" <j.lambrecht@televic.com>,
"ecos-devel@ecos.sourceware.org" <ecos-devel@ecos.sourceware.org>
Subject: RE: RFC: bsd_tcp patch on in.c
Date: Thu, 27 Jun 2013 13:43:00 -0000 [thread overview]
Message-ID: <DUB124-W1028E3B25B46E43F0508BCE4750@phx.gbl> (raw)
In-Reply-To: <51CC20E1.3090502@televic.com>
Hi Jürgen,
> The patch below we already use since 2006.
> We had problems with the TCP/IP stack directly after booting because it
> already received packets before being initialized completely.
> Here our CVS log:
>
> move
> splx(s);
> from line 682 to line 739
> so that tcp/ip stack has started up before the ethernet driver is released
> (else the not-ready stack will already receive packets)
>
> Do you agree this is a valid patch?
that is hard to tell - probably it is not necessary to lock anything here,
especially because the in_control() does many things
with the in_ifaddrhead list, without any lock. It just locks when it
adds/removes entries from that list, which is really the bare minimum.
I had similar problems however: an ICMP packet arriving while there
was zero interface addresses registered. => NULL pointer access in sys/netinet/ip_icmp.c
see the hunk at ip_icmp.c, lines 651-656. This means that the packet may
arrive well before in_ifinit is called. Even before line 293 of in.c enters the address to the list:
this place is locked with splnet however.
That null pointer access became only apparent after I changed the MMU to exclude page zero,
because usually the arm processor would silently allow read accesses to the ISR table.
See my patch at http://bugs.ecos.sourceware.org/show_bug.cgi?id=1001649 for details
on "MMU: added Access Protection against NULL-Pointer accesses".
Before I had invented that patch it was really hard to find such hideous bugs.
Regards
Bernd Edlinger
prev parent reply other threads:[~2013-06-27 13:43 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-27 11:24 Lambrecht Jürgen
2013-06-27 13:43 ` Bernd Edlinger [this message]
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