Bluetooth: L2CAP: Fix invalid response to L2CAP_ECRED_RECONF_REQ

This fixes responding with an invalid result caused by checking the
wrong size of CID which should have been (cmd_len - sizeof(*req)) and
on top of it the wrong result was use L2CAP_CR_LE_INVALID_PARAMS which
is invalid/reserved for reconf when running test like L2CAP/ECFC/BI-03-C:

> ACL Data RX: Handle 64 flags 0x02 dlen 14
      LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 6
        MTU: 64
        MPS: 64
        Source CID: 64
< ACL Data TX: Handle 64 flags 0x00 dlen 10
      LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2
!        Result: Reserved (0x000c)
         Result: Reconfiguration failed - one or more Destination CIDs invalid (0x0003)

Fiix L2CAP/ECFC/BI-04-C which expects L2CAP_RECONF_INVALID_MPS (0x0002)
when more than one channel gets its MPS reduced:

> ACL Data RX: Handle 64 flags 0x02 dlen 16
      LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 8
        MTU: 264
        MPS: 99
        Source CID: 64
!       Source CID: 65
< ACL Data TX: Handle 64 flags 0x00 dlen 10
      LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2
!        Result: Reconfiguration successful (0x0000)
         Result: Reconfiguration failed - reduction in size of MPS not allowed for more than one channel at a time (0x0002)

Fix L2CAP/ECFC/BI-05-C when SCID is invalid (85 unconnected):

> ACL Data RX: Handle 64 flags 0x02 dlen 14
      LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 6
        MTU: 65
        MPS: 64
!        Source CID: 85
< ACL Data TX: Handle 64 flags 0x00 dlen 10
      LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2
!        Result: Reconfiguration successful (0x0000)
         Result: Reconfiguration failed - one or more Destination CIDs invalid (0x0003)

Fix L2CAP/ECFC/BI-06-C when MPS < L2CAP_ECRED_MIN_MPS (64):

> ACL Data RX: Handle 64 flags 0x02 dlen 14
      LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 2 len 6
        MTU: 672
!       MPS: 63
        Source CID: 64
< ACL Data TX: Handle 64 flags 0x00 dlen 10
      LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2
!       Result: Reconfiguration failed - reduction in size of MPS not allowed for more than one channel at a time (0x0002)
        Result: Reconfiguration failed - other unacceptable parameters (0x0004)

Fix L2CAP/ECFC/BI-07-C when MPS reduced for more than one channel:

> ACL Data RX: Handle 64 flags 0x02 dlen 16
      LE L2CAP: Enhanced Credit Reconfigure Request (0x19) ident 3 len 8
        MTU: 84
!       MPS: 71
        Source CID: 64
!        Source CID: 65
< ACL Data TX: Handle 64 flags 0x00 dlen 10
      LE L2CAP: Enhanced Credit Reconfigure Respond (0x1a) ident 2 len 2
!       Result: Reconfiguration successful (0x0000)
        Result: Reconfiguration failed - reduction in size of MPS not allowed for more than one channel at a time (0x0002)

Link: bluez/bluez#1865
Fixes: 15f02b9 ("Bluetooth: L2CAP: Add initial code for Enhanced Credit Based Mode")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

Author: Vudentz

include/net/bluetooth/l2cap.h

@@ -493,6 +493,8 @@ struct l2cap_ecred_reconf_req {
 #define L2CAP_RECONF_SUCCESS		0x0000
 #define L2CAP_RECONF_INVALID_MTU	0x0001
 #define L2CAP_RECONF_INVALID_MPS	0x0002
+#define L2CAP_RECONF_INVALID_CID	0x0003
+#define L2CAP_RECONF_INVALID_PARAMS	0x0004
 
 struct l2cap_ecred_reconf_rsp {
 	__le16 result;

net/bluetooth/l2cap_core.c

@@ -5310,14 +5310,14 @@ static inline int l2cap_ecred_reconf_req(struct l2cap_conn *conn,
 	struct l2cap_ecred_reconf_req *req = (void *) data;
 	struct l2cap_ecred_reconf_rsp rsp;
 	u16 mtu, mps, result;
-	struct l2cap_chan *chan;
+	struct l2cap_chan *chan[L2CAP_ECRED_MAX_CID] = {};
 	int i, num_scid;
 
 	if (!enable_ecred)
 		return -EINVAL;
 
-	if (cmd_len < sizeof(*req) || cmd_len - sizeof(*req) % sizeof(u16)) {
-		result = L2CAP_CR_LE_INVALID_PARAMS;
+	if (cmd_len < sizeof(*req) || (cmd_len - sizeof(*req)) % sizeof(u16)) {
+		result = L2CAP_RECONF_INVALID_CID;
 		goto respond;
 	}
 
@@ -5327,42 +5327,69 @@ static inline int l2cap_ecred_reconf_req(struct l2cap_conn *conn,
 	BT_DBG("mtu %u mps %u", mtu, mps);
 
 	if (mtu < L2CAP_ECRED_MIN_MTU) {
-		result = L2CAP_RECONF_INVALID_MTU;
+		result = L2CAP_RECONF_INVALID_PARAMS;
 		goto respond;
 	}
 
 	if (mps < L2CAP_ECRED_MIN_MPS) {
-		result = L2CAP_RECONF_INVALID_MPS;
+		result = L2CAP_RECONF_INVALID_PARAMS;
 		goto respond;
 	}
 
 	cmd_len -= sizeof(*req);
 	num_scid = cmd_len / sizeof(u16);
+
+	if (num_scid > L2CAP_ECRED_MAX_CID) {
+		result = L2CAP_RECONF_INVALID_PARAMS;
+		goto respond;
+	}
+
 	result = L2CAP_RECONF_SUCCESS;
 
+	/* Check if each SCID, MTU and MPS are valid */
 	for (i = 0; i < num_scid; i++) {
 		u16 scid;
 
 		scid = __le16_to_cpu(req->scid[i]);
-		if (!scid)
-			return -EPROTO;
+		if (!scid) {
+			result = L2CAP_RECONF_INVALID_CID;
+			goto respond;
+		}
 
-		chan = __l2cap_get_chan_by_dcid(conn, scid);
-		if (!chan)
-			continue;
+		chan[i] = __l2cap_get_chan_by_dcid(conn, scid);
+		if (!chan[i]) {
+			result = L2CAP_RECONF_INVALID_CID;
+			goto respond;
+		}
 
-		/* If the MTU value is decreased for any of the included
-		 * channels, then the receiver shall disconnect all
-		 * included channels.
+		/* The MTU field shall be greater than or equal to the greatest
+		 * current MTU size of these channels.
 		 */
-		if (chan->omtu > mtu) {
-			BT_ERR("chan %p decreased MTU %u -> %u", chan,
-			       chan->omtu, mtu);
+		if (chan[i]->omtu > mtu) {
+			BT_ERR("chan %p decreased MTU %u -> %u", chan[i],
+			       chan[i]->omtu, mtu);
 			result = L2CAP_RECONF_INVALID_MTU;
+			goto respond;
 		}
 
-		chan->omtu = mtu;
-		chan->remote_mps = mps;
+		/* If more than one channel is being configured, the MPS field
+		 * shall be greater than or equal to the current MPS size of
+		 * each of these channels. If only one channel is being
+		 * configured, the MPS field may be less than the current MPS
+		 * of that channel.
+		 */
+		if (chan[i]->remote_mps >= mps && i) {
+			BT_ERR("chan %p decreased MPS %u -> %u", chan[i],
+			       chan[i]->remote_mps, mps);
+			result = L2CAP_RECONF_INVALID_MPS;
+			goto respond;
+		}
+	}
+
+	/* Commit the new MTU and MPS values after checking they are valid */
+	for (i = 0; i < num_scid; i++) {
+		chan[i]->omtu = mtu;
+		chan[i]->remote_mps = mps;
 	}
 
 respond: