linux_dsm_epyc7002/net/sctp
Daniel Borkmann b69040d8e3 net: sctp: fix panic on duplicate ASCONF chunks
When receiving a e.g. semi-good formed connection scan in the
form of ...

  -------------- INIT[ASCONF; ASCONF_ACK] ------------->
  <----------- INIT-ACK[ASCONF; ASCONF_ACK] ------------
  -------------------- COOKIE-ECHO -------------------->
  <-------------------- COOKIE-ACK ---------------------
  ---------------- ASCONF_a; ASCONF_b ----------------->

... where ASCONF_a equals ASCONF_b chunk (at least both serials
need to be equal), we panic an SCTP server!

The problem is that good-formed ASCONF chunks that we reply with
ASCONF_ACK chunks are cached per serial. Thus, when we receive a
same ASCONF chunk twice (e.g. through a lost ASCONF_ACK), we do
not need to process them again on the server side (that was the
idea, also proposed in the RFC). Instead, we know it was cached
and we just resend the cached chunk instead. So far, so good.

Where things get nasty is in SCTP's side effect interpreter, that
is, sctp_cmd_interpreter():

While incoming ASCONF_a (chunk = event_arg) is being marked
!end_of_packet and !singleton, and we have an association context,
we do not flush the outqueue the first time after processing the
ASCONF_ACK singleton chunk via SCTP_CMD_REPLY. Instead, we keep it
queued up, although we set local_cork to 1. Commit 2e3216cd54
changed the precedence, so that as long as we get bundled, incoming
chunks we try possible bundling on outgoing queue as well. Before
this commit, we would just flush the output queue.

Now, while ASCONF_a's ASCONF_ACK sits in the corked outq, we
continue to process the same ASCONF_b chunk from the packet. As
we have cached the previous ASCONF_ACK, we find it, grab it and
do another SCTP_CMD_REPLY command on it. So, effectively, we rip
the chunk->list pointers and requeue the same ASCONF_ACK chunk
another time. Since we process ASCONF_b, it's correctly marked
with end_of_packet and we enforce an uncork, and thus flush, thus
crashing the kernel.

Fix it by testing if the ASCONF_ACK is currently pending and if
that is the case, do not requeue it. When flushing the output
queue we may relink the chunk for preparing an outgoing packet,
but eventually unlink it when it's copied into the skb right
before transmission.

Joint work with Vlad Yasevich.

Fixes: 2e3216cd54 ("sctp: Follow security requirement of responding with 1 packet")
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-10-14 12:46:22 -04:00
..
associola.c net: sctp: fix panic on duplicate ASCONF chunks 2014-10-14 12:46:22 -04:00
auth.c net: sctp: cache auth_enable per endpoint 2014-04-18 18:32:00 -04:00
bind_addr.c sctp: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
chunk.c sctp: fix checkpatch errors with space required or prohibited 2013-12-26 13:47:47 -05:00
debug.c sctp: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
endpointola.c net: sctp: migrate most recently used transport to ktime 2014-06-11 12:23:17 -07:00
input.c sctp: Change sctp to implement csum_levels 2014-08-29 20:41:11 -07:00
inqueue.c sctp: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
ipv6.c sctp: Fixup v4mapped behaviour to comply with Sock API 2014-07-31 21:49:06 -07:00
Kconfig net: sctp: get rid of SCTP_DBG_TSNS entirely 2013-07-02 00:08:03 -07:00
Makefile net: sctp: Inline the functions from command.c 2014-07-08 14:38:48 -07:00
objcnt.c sctp: fix checkpatch errors with (foo*)|foo * bar|foo* bar 2013-12-26 13:47:47 -05:00
output.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-08-05 18:46:26 -07:00
outqueue.c net: sctp: Rename SCTP_XMIT_NAGLE_DELAY to SCTP_XMIT_DELAY 2014-07-22 13:32:11 -07:00
primitive.c sctp: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
probe.c sctp: loading sctp when load sctp_probe 2013-12-16 20:04:27 -05:00
proc.c snmp: fix some left over of snmp stats 2014-05-14 15:33:47 -04:00
protocol.c net/ipv4: bind ip_nonlocal_bind to current netns 2014-09-09 11:27:09 -07:00
sm_make_chunk.c net: sctp: fix skb_over_panic when receiving malformed ASCONF chunks 2014-10-14 12:46:22 -04:00
sm_sideeffect.c net: sctp: Don't transition to PF state when transport has exhausted 'Path.Max.Retrans'. 2014-04-27 23:41:14 -04:00
sm_statefuns.c net: sctp: fix skb_over_panic when receiving malformed ASCONF chunks 2014-10-14 12:46:22 -04:00
sm_statetable.c sctp: fix checkpatch errors with indent 2013-12-26 13:47:48 -05:00
socket.c net: sctp: fix ABI mismatch through sctp_assoc_to_state helper 2014-08-29 20:31:08 -07:00
ssnmap.c sctp: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
sysctl.c net: sctp: only warn in proc_sctp_do_alpha_beta if write 2014-07-02 18:44:07 -07:00
transport.c sctp: Fixup v4mapped behaviour to comply with Sock API 2014-07-31 21:49:06 -07:00
tsnmap.c sctp: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
ulpevent.c sctp: Fixup v4mapped behaviour to comply with Sock API 2014-07-31 21:49:06 -07:00
ulpqueue.c sctp: add support for busy polling to sctp protocol 2014-04-20 18:18:55 -04:00