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dccp: check sk for closed state in dccp_sendmsg()

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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 69c64866ce ("dccp: CVE-2017-8824:
use-after-free in DCCP code") is applied.

Reported-by: [email protected]
Signed-off-by: Alexey Kodanev <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
This commit is contained in:
Alexey Kodanev authored and David S. Miller committed 2018-03-07 13:38:56 -05:00
1 parent 17cfe79a65
commit 67f93df79a
1 file changed
+5
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net/dccp/proto.c
+5
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@@ -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)