Commit 8b74d439 authored Feb 12, 2017 by Eric Dumazet Committed by David S. Miller Feb 12, 2017

net/llc: avoid BUG_ON() in skb_orphan()



It seems nobody used LLC since linux-3.12.

Fortunately fuzzers like syzkaller still know how to run this code,
otherwise it would be no fun.

Setting skb->sk without skb->destructor leads to all kinds of
bugs, we now prefer to be very strict about it.

Ideally here we would use skb_set_owner() but this helper does not exist yet,
only CAN seems to have a private helper for that.

Fixes: 376c7311 ("net: add a temporary sanity check in skb_orphan()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7f677633

net/llc/llc_conn.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -821,7 +821,10 @@ void llc_conn_handler(struct llc_sap sap, struct sk_buff skb)
		* another trick required to cope with how the PROCOM state
		* machine works. -acme
		*/
		skb_orphan(skb);
		sock_hold(sk);
		skb->sk = sk;
		skb->destructor = sock_efree;
		}
		if (!sock_owned_by_user(sk))
		llc_conn_rcv(sk, skb);

net/llc/llc_sap.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -290,7 +290,10 @@ static void llc_sap_rcv(struct llc_sap sap, struct sk_buff skb,

		ev->type = LLC_SAP_EV_TYPE_PDU;
		ev->reason = 0;
		skb_orphan(skb);
		sock_hold(sk);
		skb->sk = sk;
		skb->destructor = sock_efree;
		llc_sap_state_process(sap, skb);
		}

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