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Bluetooth: l2cap: fix MPS check in l2cap_ecred_reconf_req

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The L2CAP specification states that if more than one channel is being
reconfigured, the MPS shall not be decreased. The current check has
two issues:

1) The comparison uses >= (greater-than-or-equal), which incorrectly
   rejects reconfiguration requests where the MPS stays the same.
   Since the spec says MPS "shall be greater than or equal to the
   current MPS", only a strict decrease (remote_mps > mps) should be
   rejected. Keeping the same MPS is valid.

2) The multi-channel guard uses `&& i` (loop index) to approximate
   "more than one channel", but this incorrectly allows MPS decrease
   for the first channel (i==0) even when multiple channels are being
   reconfigured. Replace with `&& num_scid > 1` which correctly
   checks whether the request covers more than one channel.

Fixes: 7accb1c432 ("Bluetooth: L2CAP: Fix invalid response to L2CAP_ECRED_RECONF_REQ")
Signed-off-by: Dudu Lu <phx0fer@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
This commit is contained in:
Dudu Lu
2026-04-15 18:43:55 +08:00
committed by Luiz Augusto von Dentz
parent 72b8deccff
commit 4f42363c81
1 changed files with 1 additions and 1 deletions
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2
net/bluetooth/l2cap_core.c
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@@ -5428,7 +5428,7 @@ static inline int l2cap_ecred_reconf_req(struct l2cap_conn *conn,
* configured, the MPS field may be less than the current MPS
* of that channel.
*/
if (chan[i]->remote_mps >= mps && i) {
if (chan[i]->remote_mps > mps && num_scid > 1) {
BT_ERR("chan %p decreased MPS %u -> %u", chan[i],
chan[i]->remote_mps, mps);
result = L2CAP_RECONF_INVALID_MPS;