This is a note to let you know that I've just added the patch titled net/llc: avoid BUG_ON() in skb_orphan() to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-llc-avoid-bug_on-in-skb_orphan.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Thu Feb 23 21:13:19 CET 2017 From: Eric Dumazet <edumazet@xxxxxxxxxx> Date: Sun, 12 Feb 2017 14:03:52 -0800 Subject: net/llc: avoid BUG_ON() in skb_orphan() From: Eric Dumazet <edumazet@xxxxxxxxxx> [ 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. Fixes: 376c7311bdb6 ("net: add a temporary sanity check in skb_orphan()") Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx> Reported-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/llc/llc_conn.c | 3 +++ net/llc/llc_sap.c | 3 +++ 2 files changed, 6 insertions(+) --- a/net/llc/llc_conn.c +++ b/net/llc/llc_conn.c @@ -821,7 +821,10 @@ void llc_conn_handler(struct llc_sap *sa * 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); --- a/net/llc/llc_sap.c +++ b/net/llc/llc_sap.c @@ -290,7 +290,10 @@ static void llc_sap_rcv(struct llc_sap * 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); } Patches currently in stable-queue which might be from edumazet@xxxxxxxxxx are queue-4.4/dccp-fix-freeing-skb-too-early-for-ipv6_recvpktinfo.patch queue-4.4/ip-fix-ip_checksum-handling.patch queue-4.4/packet-fix-races-in-fanout_add.patch queue-4.4/packet-do-not-call-fanout_release-from-atomic-contexts.patch queue-4.4/net-llc-avoid-bug_on-in-skb_orphan.patch