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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: 376c7311bd ("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>
This commit is contained in:
Eric Dumazet 2017-02-12 14:03:52 -08:00 committed by David S. Miller
parent 7f67763337
commit 8b74d439e1
2 changed files with 6 additions and 0 deletions
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3
net/llc/llc_conn.c
View File

@ -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 * another trick required to cope with how the PROCOM state
* machine works. -acme * machine works. -acme
*/ */
skb_orphan(skb);
sock_hold(sk);
skb->sk = sk; skb->sk = sk;
skb->destructor = sock_efree;
} }
if (!sock_owned_by_user(sk)) if (!sock_owned_by_user(sk))
llc_conn_rcv(sk, skb); llc_conn_rcv(sk, skb);

3
net/llc/llc_sap.c
View File

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