From 42b52783a59cc706c71cdc7096edce4a6f086fd3 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 12 Feb 2017 14:03:52 -0800 Subject: [PATCH] net/llc: avoid BUG_ON() in skb_orphan() [ Upstream commit 8b74d439e1697110c5e5c600643e823eb1dd0762 ] 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. CVE: CVE-2017-6345 Upstream-Status: Backport [from kernel.org longterm 4.9.52] Fixes: 376c7311bdb6 ("net: add a temporary sanity check in skb_orphan()") Signed-off-by: Eric Dumazet Reported-by: Andrey Konovalov Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sona Sarmadi --- net/llc/llc_conn.c | 3 +++ net/llc/llc_sap.c | 3 +++ 2 files changed, 6 insertions(+) diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c index 3e821da..8bc5a1b 100644 --- a/net/llc/llc_conn.c +++ b/net/llc/llc_conn.c @@ -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); diff --git a/net/llc/llc_sap.c b/net/llc/llc_sap.c index d0e1e80..5404d0d 100644 --- a/net/llc/llc_sap.c +++ b/net/llc/llc_sap.c @@ -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); } -- 1.9.1