Subject: [PATCH net 0/4] net/sched: forbid 'goto_chain' on fallback actions

From: Davide Caratti <[email-masked]>
Date: Sat, 20 Oct 2018 23:33:06 +0200

the following command:

 # tc actions add action police rate 1mbit burst 1k conform-exceed \
 > pass / goto chain 42

generates a NULL pointer dereference when packets exceed the configured
rate. Similarly, the following command:

 # tc actions add action pass random determ goto chain 42 2

makes the kernel crash with NULL dereference when the first packet does
not match the 'pass' action.

gact and police allow users to specify a fallback control action, that is
stored in the action private data. 'goto chain x' never worked for these
cases, since a->goto_chain handle was never initialized. There is only one
goto_chain handle per TC action, and it is designed to be non-NULL only if
tcf_action contains a 'goto chain' command. So, let's forbid 'goto chain'
on fallback actions.

Patch 1/4 and 2/4 change the .init() functions of police and gact, to let
them return an error when users try to set 'goto chain x' in the fallback
action. Patch 3/4 and 4/4 add TDC selftest coverage to this new behavior. 

Davide Caratti (4):
  net/sched: act_gact: disallow 'goto chain' on fallback control action
  net/sched: act_police: disallow 'goto chain' on fallback control
    action
  tc-tests: test denial of 'goto chain' on 'random' traffic in gact.json
  tc-tests: test denial of 'goto chain' for exceed traffic in
    police.json

 net/sched/act_gact.c                          |  5 ++++
 net/sched/act_police.c                        | 12 ++++++++--
 .../tc-testing/tc-tests/actions/gact.json     | 24 +++++++++++++++++++
 .../tc-testing/tc-tests/actions/police.json   | 24 +++++++++++++++++++
 4 files changed, 63 insertions(+), 2 deletions(-)

-- 
2.17.1