mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction

Browse source

mptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce,
backup, join_id, token and msk from the saved cookie entry when rebuilding
the request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it
does not restore local_id, even though the SYN path saved it.
subflow_ulp_clone() then reads that uninitialized field and stores it as
the joined subflow's address-ID. Because the request-sock slab is
SLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale
byte of a previously freed request socket, which an off-path peer can
influence by sending concurrent MP_JOIN SYNs. This corrupts the path
manager's id-based subflow bookkeeping for the connection.

Restore subflow_req->local_id from the cookie entry, as done for the other
fields.

Fixes: 9466a1cceb ("mptcp: enable JOIN requests even if cookies are in use")
Cc: stable@vger.kernel.org
Signed-off-by: Harshit Varu <harshitvaru666@gmail.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260815115205.197151-1-harshitvaru666@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

This commit is contained in:

Harshit Varu 2026-08-15 17:22:05 +05:30 • committed by Jakub Kicinski

parent 5e8076e4e4

commit b878dfdd12

1 changed files with 1 additions and 0 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

1

net/mptcp/syncookies.c

View file