4.9-stable review patch. If anyone has any objections, please let me know.
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From: Alexey Kodanev alexey.kodanev@oracle.com
[ Upstream commit 67f93df79aeefc3add4e4b31a752600f834236e2 ]
dccp_disconnect() sets 'dp->dccps_hc_tx_ccid' tx handler to NULL, therefore if DCCP socket is disconnected and dccp_sendmsg() is called after it, it will cause a NULL pointer dereference in dccp_write_xmit().
This crash and the reproducer was reported by syzbot. Looks like it is reproduced if commit 69c64866ce07 ("dccp: CVE-2017-8824: use-after-free in DCCP code") is applied.
Reported-by: syzbot+f99ab3887ab65d70f816@syzkaller.appspotmail.com Signed-off-by: Alexey Kodanev alexey.kodanev@oracle.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/dccp/proto.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/net/dccp/proto.c +++ b/net/dccp/proto.c @@ -789,6 +789,11 @@ int dccp_sendmsg(struct sock *sk, struct if (skb == NULL) goto out_release;
+ if (sk->sk_state == DCCP_CLOSED) { + rc = -ENOTCONN; + goto out_discard; + } + skb_reserve(skb, sk->sk_prot->max_header); rc = memcpy_from_msg(skb_put(skb, len), msg, len); if (rc != 0)