[PATCH v2 2/2] Bluetooth: L2CAP: skip ERTM re-init on repeated CONFIG_RSP

[Michael Bommarito <michael.bommarito@gmail.com>]

commit 25f420a0d4cf ("Bluetooth: L2CAP: Fix ERTM re-init and zero
pdu_len infinite loop") taught l2cap_config_req() not to call
l2cap_ertm_init() again once the channel is already in BT_CONNECTED.

l2cap_config_rsp() still lacks the same guard. After the initial ERTM
setup, any extra successful CONFIG_RSP re-enters l2cap_ertm_init(),
reinitializes tx_q and srej_q, and allocates fresh sequence lists over
the existing channel state.

Mirror the existing BT_CONNECTED check in l2cap_config_rsp() so response
parsing can still update negotiated parameters without reinitializing
ERTM state or leaking the old resources.

Cc: stable@vger.kernel.org
Signed-off-by: Michael Bommarito <michael.bommarito@gmail.com>
Assisted-by: Claude:claude-opus-4-7
---
Changes in v2:
- split out of the original zero-txwin patch so the repeated
  `CONFIG_RSP` ERTM re-init bug is reviewed as a distinct issue
- mirror the existing `BT_CONNECTED` guard already present on the
  `CONFIG_REQ` side after commit 25f420a0d4cf

 net/bluetooth/l2cap_core.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 7ffafd117817..fe98f4821a90 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4480,14 +4480,16 @@ static inline int l2cap_config_rsp(struct l2cap_conn *conn,
 	if (test_bit(CONF_OUTPUT_DONE, &chan->conf_state)) {
 		set_default_fcs(chan);
 
-		if (chan->mode == L2CAP_MODE_ERTM ||
-		    chan->mode == L2CAP_MODE_STREAMING)
-			err = l2cap_ertm_init(chan);
+		if (chan->state != BT_CONNECTED) {
+			if (chan->mode == L2CAP_MODE_ERTM ||
+			    chan->mode == L2CAP_MODE_STREAMING)
+				err = l2cap_ertm_init(chan);
 
-		if (err < 0)
-			l2cap_send_disconn_req(chan, -err);
-		else
-			l2cap_chan_ready(chan);
+			if (err < 0)
+				l2cap_send_disconn_req(chan, -err);
+			else
+				l2cap_chan_ready(chan);
+		}
 	}
 
 done:
-- 
2.53.0