Commit 351050ec authored Aug 30, 2017 by Eric Dumazet Committed by David S. Miller Aug 30, 2017

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: ab7ac4eb ("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>

parent f5c3dd4b

net/kcm/kcmsock.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -1383,6 +1383,10 @@ static int kcm_attach(struct socket sock, struct socket csock,
		if (!csk)
		return -EINVAL;

		/* We must prevent loops or risk deadlock ! */
		if (csk->sk_family == PF_KCM)
		return -EOPNOTSUPP;

		psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL);
		if (!psock)
		return -ENOMEM;