On Thu, Jan 05, 2017 at 05:45:29PM -0800, Jarno Rajahalme wrote:
>
> > On Jan 5, 2017, at 4:48 PM, Ben Pfaff <b...@ovn.org> wrote:
> >
> > On Thu, Jan 05, 2017 at 04:03:17PM -0800, Jarno Rajahalme wrote:
> >>
> >>> On Jan 4, 2017, at 11:03 PM, Ben Pfaff <b...@ovn.org> wrote:
> >>>
> >>> On Wed, Jan 04, 2017 at 07:21:44PM -0800, Jarno Rajahalme wrote:
> >>>>
> >>>>> On Dec 21, 2016, at 2:36 PM, Ben Pfaff <b...@ovn.org> wrote:
> >>>>>
> >>>>> On Wed, Dec 07, 2016 at 04:49:00PM -0800, Jarno Rajahalme wrote:
> >>>>> I'd be more comfortable if nx_stack_pop() had assertions to check for
> >>>>> underflow.
> >>>>
> >>>> I don’t think OVS should assert fail if controller issues one pop
> >>>> too many? Do you mean that current users of nx_stack_pop() do not
> >>>> check for NULL return? I had a look and think that setting “*bytes”
> >>>> to zero when returning NULL should be enough for all users.
> >>>
> >>> It appears to me that if stack->size is greater than 0 but less than the
> >>> number of bytes indicated by its last byte, then it will corrupt the
> >>> ofpbuf size and that this will later cause some kind of failure that
> >>> will be harder to debug than an assertion failure.
> >>>
> >>
> >> OK, now i got it. This is just to guard against (future) bugs in OVS
> >> itself.
> >
> > Yes.
> >
> >>>>> In ofputil_decode_packet_in_private(), it's probably worth checking the
> >>>>> format of the stack we pull from the payload, since a badly formatted
> >>>>> stack can segfault us (if we leave out assertions) or assert-fail us (if
> >>>>> we include them).
> >>>>>
> >>>>
> >>>> What do you mean with badly formatted stack? Zero-sized property? IMO
> >>>> even that would be properly pushed and popped from the stack, storing
> >>>> only the length (of zero) in the stack.
> >>>
> >>> I mean that if the property contains, for example, a single byte with
> >>> value 0xff, then it's badly formatted because we can pop off a length
> >>> (255) but then popping off that number of bytes will underflow.
> >>
> >> I did not change the encoding of the stack as properties, so each
> >> value in the stack is still encoded as a separate property, where the
> >> (aligned) value length is used as the property length.
> >
> > I guess I forgot that.
> >
> > Thanks, that's fine then.
> >
> >> ofpprop_pull() does the length checking for the properties and the
> >> current code in ofputil_decode_packet_in_private() assert fails on any
> >> error, which is not good, as a controller bug would crash OVS?
> >
> > That's bad. Maybe the fix is as simple as this, though.
> >
> > diff --git a/lib/ofp-util.c b/lib/ofp-util.c
> > index 156d8d2..421b9d7 100644
> > --- a/lib/ofp-util.c
> > +++ b/lib/ofp-util.c
> > @@ -1,5 +1,5 @@
> > /*
> > - * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016
> > Nicira, Inc.
> > + * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016,
> > 2017 Nicira, Inc.
> > *
> > * Licensed under the Apache License, Version 2.0 (the "License");
> > * you may not use this file except in compliance with the License.
> > @@ -4061,7 +4061,9 @@ ofputil_decode_packet_in_private(const struct
> > ofp_header *oh, bool loose,
> > uint64_t type;
> >
> > error = ofpprop_pull(&continuation, &payload, &type);
> > - ovs_assert(!error);
> > + if (error) {
> > + break;
> > + }
> >
> > switch (type) {
> > case NXCPT_BRIDGE:
> > @@ -4124,7 +4126,7 @@ ofputil_decode_packet_in_private(const struct
> > ofp_header *oh, bool loose,
> > ofputil_packet_in_private_destroy(pin);
> > }
> >
> > - return 0;
> > + return error;
> > }
> >
> > /* Frees data in 'pin' that is dynamically allocated by
> >
>
> I folded this in to v3.
This bug is in 2.6, isn't it? If so then we should fix it in a separate
patch, for backporting purposes.
_______________________________________________
dev mailing list
d...@openvswitch.org
https://mail.openvswitch.org/mailman/listinfo/ovs-dev
