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[net-next,0/4] kcm: Fix two locking issues

Message ID 20171222194755.8544-1-tom@quantonium.net
Headers show
Series kcm: Fix two locking issues | expand

Message

Tom Herbert Dec. 22, 2017, 7:47 p.m. UTC 
One issue is lockdep warnings when sock_owned_by_user returns true
in strparser. Fix is to add and call sock_owned_by_user_nocheck since
the check for owned by user is not an error condition in this case.

The other issue is a potential deadlock between TX and RX paths

KCM socket lock and the psock socket lock are acquired in both
the RX and TX path, however they take the locks in opposite order
which can lead to deadlock. The fix is to add try_sock_lock to see
if psock socket lock can get acquired in the TX path with KCM lock
held. If not, then KCM socket is released and the psock socket lock
and KCM socket lock are acquired in the same order as the RX path.

Tested:

Ran KCM traffic without incident.

Tom Herbert (4):
  sock: Add sock_owned_by_user_nocheck
  strparser: Call sock_owned_by_user_nocheck
  sock_lock: Add try_sock_lock
  kcm: Address deadlock between TX and RX paths

 include/net/kcm.h         |  1 +
 include/net/sock.h        | 12 +++++++++
 net/core/sock.c           | 20 +++++++++++++++
 net/kcm/kcmsock.c         | 64 ++++++++++++++++++++++++++++++++++-------------
 net/strparser/strparser.c |  2 +-
 5 files changed, 81 insertions(+), 18 deletions(-)