From 0a8e987dcc13244b5a5bc90cb1b184f813104d87 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Thu, 2 Nov 2023 14:05:48 -0700 Subject: tcp: Fix SYN option room calculation for TCP-AO. When building SYN packet in tcp_syn_options(), MSS, TS, WS, and SACKPERM are used without checking the remaining bytes in the options area. To keep that logic as is, we limit the TCP-AO MAC length in tcp_ao_parse_crypto(). Currently, the limit is calculated as below. MAX_TCP_OPTION_SPACE - TCPOLEN_TSTAMP_ALIGNED - TCPOLEN_WSCALE_ALIGNED - TCPOLEN_SACKPERM_ALIGNED This looks confusing as (1) we pack SACKPERM into the leading 2-bytes of the aligned 12-bytes of TS and (2) TCPOLEN_MSS_ALIGNED is not used. Fortunately, the calculated limit is not wrong as TCPOLEN_SACKPERM_ALIGNED and TCPOLEN_MSS_ALIGNED are the same value. However, we should use the proper constant in the formula. MAX_TCP_OPTION_SPACE - TCPOLEN_MSS_ALIGNED - TCPOLEN_TSTAMP_ALIGNED - TCPOLEN_WSCALE_ALIGNED Fixes: 4954f17ddefc ("net/tcp: Introduce TCP_AO setsockopt()s") Signed-off-by: Kuniyuki Iwashima Reviewed-by: Dmitry Safonov Signed-off-by: David S. Miller --- net/ipv4/tcp_ao.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/ipv4') diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index ef5472ed6158..7696417d0640 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -1315,7 +1315,8 @@ static int tcp_ao_parse_crypto(struct tcp_ao_add *cmd, struct tcp_ao_key *key) key->maclen = cmd->maclen ?: 12; /* 12 is the default in RFC5925 */ /* Check: maclen + tcp-ao header <= (MAX_TCP_OPTION_SPACE - mss - * - tstamp - wscale - sackperm), + * - tstamp (including sackperm) + * - wscale), * see tcp_syn_options(), tcp_synack_options(), commit 33ad798c924b. * * In order to allow D-SACK with TCP-AO, the header size should be: @@ -1342,9 +1343,9 @@ static int tcp_ao_parse_crypto(struct tcp_ao_add *cmd, struct tcp_ao_key *key) * large to leave sufficient option space. */ syn_tcp_option_space = MAX_TCP_OPTION_SPACE; + syn_tcp_option_space -= TCPOLEN_MSS_ALIGNED; syn_tcp_option_space -= TCPOLEN_TSTAMP_ALIGNED; syn_tcp_option_space -= TCPOLEN_WSCALE_ALIGNED; - syn_tcp_option_space -= TCPOLEN_SACKPERM_ALIGNED; if (tcp_ao_len(key) > syn_tcp_option_space) { err = -EMSGSIZE; goto err_kfree; -- cgit