Commit 67f93df7 authored by Alexey Kodanev's avatar Alexey Kodanev Committed by David S. Miller

dccp: check sk for closed state in dccp_sendmsg()

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 69c64866 ("dccp: CVE-2017-8824:
use-after-free in DCCP code") is applied.

Reported-by: syzbot+f99ab3887ab65d70f816@syzkaller.appspotmail.com
Signed-off-by: default avatarAlexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 17cfe79a
......@@ -794,6 +794,11 @@ int dccp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
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)
......
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