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 _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev