The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 8031b58c3a9b1db3ef68b3bd749fbee2e1e1aaa3 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2024061719-prewashed-wimp-a695@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

8031b58c3a9b ("mptcp: ensure snd_una is properly initialized on connect") fb7a0d334894 ("mptcp: ensure snd_nxt is properly initialized on connect") 54f1944ed6d2 ("mptcp: factor out mptcp_connect()") a42cf9d18278 ("mptcp: poll allow write call before actual connect") d98a82a6afc7 ("mptcp: handle defer connect in mptcp_sendmsg") 3e5014909b56 ("mptcp: cleanup MPJ subflow list handling") 3d1d6d66e156 ("mptcp: implement support for user-space disconnect") b29fcfb54cd7 ("mptcp: full disconnect implementation") 3ce0852c86b9 ("mptcp: enforce HoL-blocking estimation") 7cd2802d7496 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8031b58c3a9b1db3ef68b3bd749fbee2e1e1aaa3 Mon Sep 17 00:00:00 2001 From: Paolo Abeni pabeni@redhat.com Date: Fri, 7 Jun 2024 17:01:48 +0200 Subject: [PATCH] mptcp: ensure snd_una is properly initialized on connect

This is strictly related to commit fb7a0d334894 ("mptcp: ensure snd_nxt is properly initialized on connect"). It turns out that syzkaller can trigger the retransmit after fallback and before processing any other incoming packet - so that snd_una is still left uninitialized.

Address the issue explicitly initializing snd_una together with snd_nxt and write_seq.

Suggested-by: Mat Martineau martineau@kernel.org Fixes: 8fd738049ac3 ("mptcp: fallback in case of simultaneous connect") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch cpaasch@apple.com Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/485 Signed-off-by: Paolo Abeni pabeni@redhat.com Reviewed-by: Mat Martineau martineau@kernel.org Signed-off-by: Matthieu Baerts (NGI0) matttbe@kernel.org Link: https://lore.kernel.org/r/20240607-upstream-net-20240607-misc-fixes-v1-1-1ab... Signed-off-by: Jakub Kicinski kuba@kernel.org

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 96b113854bd3..bb7dca8aa2d9 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -3740,6 +3740,7 @@ static int mptcp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)

WRITE_ONCE(msk->write_seq, subflow->idsn); WRITE_ONCE(msk->snd_nxt, subflow->idsn); + WRITE_ONCE(msk->snd_una, subflow->idsn); if (likely(!__mptcp_check_fallback(msk))) MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVE);