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dccp: check sk for closed state in dccp_sendmsg() 

commit 67f93df79aeefc3add4e4b31a752600f834236e2 upstream.

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: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Alexey Kodanev 2018-03-06 22:57:01 +03:00 committed by syphyr
parent 2fd7da79af
commit 3f12b0feeb
1 changed files with 5 additions and 0 deletions
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5
net/dccp/proto.c
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@ -785,6 +785,11 @@ int dccp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
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_fromiovec(skb_put(skb, len), msg->msg_iov, len);
if (rc != 0)