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Bluetooth: L2CAP: Fix not checking output MTU is acceptable on L2CAP_ECRED_CONN_REQ 

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: 15f02b9105 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Luiz Augusto von Dentz 2026-02-17 13:29:43 -05:00
parent 7cff9a40c6
commit a8d1d73c81
2 changed files with 19 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
net/bluetooth/l2cap_core.c
View File

@ -5117,6 +5117,14 @@ 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++) {

15
net/bluetooth/l2cap_sock.c
View File

@ -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: