Re: [PATCH] tcp: Reject invalid ack_seq to Fast Open sockets
flat view
From: David Miller <davem@davemloft.net>
Date: 2012-10-23 06:43:48
From: "H.K. Jerry Chu" <redacted> Date: Mon, 22 Oct 2012 14:26:36 -0700
From: Jerry Chu <redacted> A packet with an invalid ack_seq may cause a TCP Fast Open socket to switch to the unexpected TCP_CLOSING state, triggering a BUG_ON kernel panic. When a FIN packet with an invalid ack_seq# arrives at a socket in the TCP_FIN_WAIT1 state, rather than discarding the packet, the current code will accept the FIN, causing state transition to TCP_CLOSING. This may be a small deviation from RFC793, which seems to say that the packet should be dropped. Unfortunately I did not expect this case for Fast Open hence it will trigger a BUG_ON panic. It turns out there is really nothing bad about a TFO socket going into TCP_CLOSING state so I could just remove the BUG_ON statements. But after some thought I think it's better to treat this case like TCP_SYN_RECV and return a RST to the confused peer who caused the unacceptable ack_seq to be generated in the first place. Signed-off-by: H.K. Jerry Chu <redacted>
Applied, thanks.
quoted hunk ↗ jump to hunk
- BUG_ON(sk->sk_state != TCP_SYN_RECV && + WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && sk->sk_state != TCP_FIN_WAIT1);
I fixed up the indentation of the second line of the test when I applied this.