kcm: do not attach PF_KCM sockets to avoid deadlock
authorEric Dumazet <edumazet@google.com>
Wed, 30 Aug 2017 16:29:31 +0000 (09:29 -0700)
committerDavid S. Miller <davem@davemloft.net>
Wed, 30 Aug 2017 22:55:10 +0000 (15:55 -0700)
commit351050ecd6523374b370341cc29fe61e2201556b
tree5b6c0a72dcf7b3d172c2be867e5bf2fd10030099
parentf5c3dd4b5363af997d418174d578a795081aab51
kcm: do not attach PF_KCM sockets to avoid deadlock

syzkaller had no problem to trigger a deadlock, attaching a KCM socket
to another one (or itself). (original syzkaller report was a very
confusing lockdep splat during a sendmsg())

It seems KCM claims to only support TCP, but no enforcement is done,
so we might need to add additional checks.

Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Tom Herbert <tom@quantonium.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/kcm/kcmsock.c