[PATCH net v4 0/4] net: bpfilter: fix two bugs in bpfilter

[Taehee Yoo <ap420073@gmail.com>]

This patches fix two bugs in the bpfilter_umh which are related in
iptables command.

The first patch adds an exit code for UMH process.
This provides an opportunity to cleanup members of the umh_info
to modules which use the UMH.
In order to identify UMH processes, a new flag PF_UMH is added.

The second patch makes the bpfilter_umh use UMH cleanup callback.

The third patch adds re-start routine for the bpfilter_umh.
The bpfilter_umh does not re-start after error occurred.
because there is no re-start routine in the module.

The fourth patch ensures that the bpfilter.ko module will not removed while
it's being used.
The bpfilter.ko is not protected by locks or module reference counter.
Therefore that can be removed while module is being used.
In order to protect that, mutex is used.

The first and second patch are preparation patches for the third and
fourth patch.

TEST #1
   while :
   do
	modprobe bpfilter
	kill -9 <pid of the bpfilter_umh>
	iptables -vnL
   done

TEST #2
   while :
   do
	iptables -I FORWARD -m string --string ap --algo kmp &
	iptables -F &
	modprobe -rv bpfilter &
   done

TEST #3
   while :
   do
	modprobe bpfilter &
	modprobe -rv bpfilter &
   done

The TEST1 makes a failure of iptables command.
This is fixed by the third patch.

The TEST2 makes a panic because of a race condition in the bpfilter_umh
module.
This is fixed by the fourth patch.

The TEST3 makes a double-create UMH process.
This is fixed by the third and fourth patch.

v4 :
 - declare the exit_umh() as static inline
 - check stop flag in the load_umh() to avoid a double-create UMH
v3 :
 - Avoid unnecessary list lookup for non-UMH processes
 - Add a new PF_UMH flag
v2 : add the first and second patch
v1 : Initial patch

Taehee Yoo (4):
  umh: add exit routine for UMH process
  net: bpfilter: use cleanup callback to release umh_info
  net: bpfilter: restart bpfilter_umh when error occurred
  net: bpfilter: disallow to remove bpfilter module while being used

 include/linux/bpfilter.h         | 15 +++++--
 include/linux/sched.h            |  9 ++++
 include/linux/umh.h              |  2 +
 kernel/exit.c                    |  1 +
 kernel/umh.c                     | 33 +++++++++++++-
 net/bpfilter/bpfilter_kern.c     | 76 ++++++++++++++++++--------------
 net/bpfilter/bpfilter_umh_blob.S |  2 +-
 net/ipv4/bpfilter/sockopt.c      | 58 +++++++++++++++++++-----
 8 files changed, 146 insertions(+), 50 deletions(-)

-- 
2.17.1