This is a note to let you know that I've just added the patch titled mptcp: fix length of ADD_ADDR with port sub-option to the 5.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mptcp-fix-length-of-add_addr-with-port-sub-option.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 27ab92d9996e4e003a726d22c56d780a1655d6b4 Mon Sep 17 00:00:00 2001 From: Davide Caratti <dcaratti@xxxxxxxxxx> Date: Mon, 8 Mar 2021 10:00:04 +0100 Subject: mptcp: fix length of ADD_ADDR with port sub-option MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Davide Caratti <dcaratti@xxxxxxxxxx> commit 27ab92d9996e4e003a726d22c56d780a1655d6b4 upstream. in current Linux, MPTCP peers advertising endpoints with port numbers use a sub-option length that wrongly accounts for the trailing TCP NOP. Also, receivers will only process incoming ADD_ADDR with port having such wrong sub-option length. Fix this, making ADD_ADDR compliant to RFC8684 §3.4.1. this can be verified running tcpdump on the kselftests artifacts: unpatched kernel: [root@bottarga mptcp]# tcpdump -tnnr unpatched.pcap | grep add-addr reading from file unpatched.pcap, link-type LINUX_SLL (Linux cooked v1), snapshot length 65535 IP 10.0.1.1.10000 > 10.0.1.2.53078: Flags [.], ack 101, win 509, options [nop,nop,TS val 214459678 ecr 521312851,mptcp add-addr v1 id 1 a00:201:2774:2d88:7436:85c3:17fd:101], length 0 IP 10.0.1.2.53078 > 10.0.1.1.10000: Flags [.], ack 101, win 502, options [nop,nop,TS val 521312852 ecr 214459678,mptcp add-addr[bad opt]] patched kernel: [root@bottarga mptcp]# tcpdump -tnnr patched.pcap | grep add-addr reading from file patched.pcap, link-type LINUX_SLL (Linux cooked v1), snapshot length 65535 IP 10.0.1.1.10000 > 10.0.1.2.38178: Flags [.], ack 101, win 509, options [nop,nop,TS val 3728873902 ecr 2732713192,mptcp add-addr v1 id 1 10.0.2.1:10100 hmac 0xbccdfcbe59292a1f,nop,nop], length 0 IP 10.0.1.2.38178 > 10.0.1.1.10000: Flags [.], ack 101, win 502, options [nop,nop,TS val 2732713195 ecr 3728873902,mptcp add-addr v1-echo id 1 10.0.2.1:10100,nop,nop], length 0 Fixes: 22fb85ffaefb ("mptcp: add port support for ADD_ADDR suboption writing") CC: stable@xxxxxxxxxxxxxxx # 5.11+ Reviewed-by: Mat Martineau <mathew.j.martineau@xxxxxxxxxxxxxxx> Acked-and-tested-by: Geliang Tang <geliangtang@xxxxxxxxx> Signed-off-by: Davide Caratti <dcaratti@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mptcp/protocol.h | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -50,14 +50,15 @@ #define TCPOLEN_MPTCP_DSS_MAP64 14 #define TCPOLEN_MPTCP_DSS_CHECKSUM 2 #define TCPOLEN_MPTCP_ADD_ADDR 16 -#define TCPOLEN_MPTCP_ADD_ADDR_PORT 20 +#define TCPOLEN_MPTCP_ADD_ADDR_PORT 18 #define TCPOLEN_MPTCP_ADD_ADDR_BASE 8 -#define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT 12 +#define TCPOLEN_MPTCP_ADD_ADDR_BASE_PORT 10 #define TCPOLEN_MPTCP_ADD_ADDR6 28 -#define TCPOLEN_MPTCP_ADD_ADDR6_PORT 32 +#define TCPOLEN_MPTCP_ADD_ADDR6_PORT 30 #define TCPOLEN_MPTCP_ADD_ADDR6_BASE 20 -#define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT 24 -#define TCPOLEN_MPTCP_PORT_LEN 4 +#define TCPOLEN_MPTCP_ADD_ADDR6_BASE_PORT 22 +#define TCPOLEN_MPTCP_PORT_LEN 2 +#define TCPOLEN_MPTCP_PORT_ALIGN 2 #define TCPOLEN_MPTCP_RM_ADDR_BASE 4 #define TCPOLEN_MPTCP_FASTCLOSE 12 @@ -587,8 +588,9 @@ static inline unsigned int mptcp_add_add len = TCPOLEN_MPTCP_ADD_ADDR6_BASE; if (!echo) len += MPTCPOPT_THMAC_LEN; + /* account for 2 trailing 'nop' options */ if (port) - len += TCPOLEN_MPTCP_PORT_LEN; + len += TCPOLEN_MPTCP_PORT_LEN + TCPOLEN_MPTCP_PORT_ALIGN; return len; } Patches currently in stable-queue which might be from dcaratti@xxxxxxxxxx are queue-5.11/mptcp-fix-length-of-add_addr-with-port-sub-option.patch