From df791c24f561f389fbc05d014f3404113688ef3c Mon Sep 17 00:00:00 2001 From: Luiz Augusto von Dentz Date: Tue, 17 Feb 2026 13:29:43 -0500 Subject: [PATCH] Bluetooth: L2CAP: Fix not checking output MTU is acceptable on L2CAP_ECRED_CONN_REQ [ Upstream commit a8d1d73c81d1e70d2aa49fdaf59d933bb783ffe5 ] Upon receiving L2CAP_ECRED_CONN_REQ the given MTU shall be checked against the suggested MTU of the listening socket as that is required by the likes of PTS L2CAP/ECFC/BV-27-C test which expects L2CAP_CR_LE_UNACCEPT_PARAMS if the MTU is lowers than socket omtu. In order to be able to set chan->omtu the code now allows setting setsockopt(BT_SNDMTU), but it is only allowed when connection has not been stablished since there is no procedure to reconfigure the output MTU. Link: https://github.com/bluez/bluez/issues/1895 Fixes: 15f02b910562 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode") Signed-off-by: Luiz Augusto von Dentz Signed-off-by: Sasha Levin --- net/bluetooth/l2cap_core.c | 8 ++++++++ net/bluetooth/l2cap_sock.c | 15 +++++++++++---- 2 files changed, 19 insertions(+), 4 deletions(-) diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c index a5038160675ea..29af3f63e89ce 100644 --- a/net/bluetooth/l2cap_core.c +++ b/net/bluetooth/l2cap_core.c @@ -5101,6 +5101,14 @@ static inline int l2cap_ecred_conn_req(struct l2cap_conn *conn, goto unlock; } + /* Check if the listening channel has set an output MTU then the + * requested MTU shall be less than or equal to that value. + */ + if (pchan->omtu && mtu < pchan->omtu) { + result = L2CAP_CR_LE_UNACCEPT_PARAMS; + goto unlock; + } + result = L2CAP_CR_LE_SUCCESS; for (i = 0; i < num_scid; i++) { diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c index 9ee189c815d49..66ab2754594d6 100644 --- a/net/bluetooth/l2cap_sock.c +++ b/net/bluetooth/l2cap_sock.c @@ -1029,10 +1029,17 @@ static int l2cap_sock_setsockopt(struct socket *sock, int level, int optname, break; } - /* Setting is not supported as it's the remote side that - * decides this. - */ - err = -EPERM; + /* Only allow setting output MTU when not connected */ + if (sk->sk_state == BT_CONNECTED) { + err = -EISCONN; + break; + } + + err = copy_safe_from_sockptr(&mtu, sizeof(mtu), optval, optlen); + if (err) + break; + + chan->omtu = mtu; break; case BT_RCVMTU: -- 2.47.3