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mptcp: avoid a WARN on bad input. 

Syzcaller has found a way to trigger the WARN_ON_ONCE condition
in check_fully_established().

The root cause is a legit fallback to TCP scenario, so replace
the WARN with a plain message on a more strict condition.

Fixes: f296234c98 ("mptcp: Add handling of incoming MP_JOIN requests")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2020-04-30 15:01:53 +02:00 committed by David S. Miller
parent cfde141ea3
commit d6085fe19b
1 changed files with 2 additions and 2 deletions
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4
net/mptcp/options.c
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@ -703,8 +703,6 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
goto fully_established;
}
WARN_ON_ONCE(subflow->can_ack);
/* If the first established packet does not contain MP_CAPABLE + data
* then fallback to TCP
*/
@ -714,6 +712,8 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *sk,
return false;
}
if (unlikely(!READ_ONCE(msk->pm.server_side)))
pr_warn_once("bogus mpc option on established client sk");
subflow->fully_established = 1;
subflow->remote_key = mp_opt->sndr_key;
subflow->can_ack = 1;