Commit 2c1f97a5 authored by Arthur Mongodin's avatar Arthur Mongodin Committed by Paolo Abeni
Browse files

mptcp: Fix data stream corruption in the address announcement 



Because of the size restriction in the TCP options space, the MPTCP
ADD_ADDR option is exclusive and cannot be sent with other MPTCP ones.
For this reason, in the linked mptcp_out_options structure, group of
fields linked to different options are part of the same union.

There is a case where the mptcp_pm_add_addr_signal() function can modify
opts->addr, but not ended up sending an ADD_ADDR. Later on, back in
mptcp_established_options, other options will be sent, but with
unexpected data written in other fields due to the union, e.g. in
opts->ext_copy. This could lead to a data stream corruption in the next
packet.

Using an intermediate variable, prevents from corrupting previously
established DSS option. The assignment of the ADD_ADDR option
parameters is now done once we are sure this ADD_ADDR option can be set
in the packet, e.g. after having dropped other suboptions.

Fixes: 1bff1e43 ("mptcp: optimize out option generation")
Cc: stable@vger.kernel.org
Suggested-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarArthur Mongodin <amongodin@randorisec.fr>
Reviewed-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
[ Matt: the commit message has been updated: long lines splits and some
  clarifications. ]
Signed-off-by: default avatarMatthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250314-net-mptcp-fix-data-stream-corr-sockopt-v1-1-122dbb249db3@kernel.org


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent f31b6fbf

net/mptcp/options.c

+4 −2
Original line number Diff line number Diff line
@@ -651,6 +651,7 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * 
	struct mptcp_sock *msk = mptcp_sk(subflow->conn);

	bool drop_other_suboptions = false;

	unsigned int opt_size = *size;

	struct mptcp_addr_info addr;

	bool echo;

	int len;
@@ -659,7 +660,7 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * 
	 */

	if (!mptcp_pm_should_add_signal(msk) ||

	    (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) ||

	    !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &opts->addr,

	    !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &addr,

		    &echo, &drop_other_suboptions))

		return false;
@@ -672,7 +673,7 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * 
	else if (opts->suboptions & OPTION_MPTCP_DSS)

		return false;



	len = mptcp_add_addr_len(opts->addr.family, echo, !!opts->addr.port);

	len = mptcp_add_addr_len(addr.family, echo, !!addr.port);

	if (remaining < len)

		return false;
@@ -689,6 +690,7 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * 
		opts->ahmac = 0;

		*size -= opt_size;

	}

	opts->addr = addr;

	opts->suboptions |= OPTION_MPTCP_ADD_ADDR;

	if (!echo) {

		MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ADDADDRTX);