[SRU Bionic v3 1/2] Bluetooth: L2CAP: Fix accepting connection request for invalid SPSM

[Cengiz Can]

From: Luiz Augusto von Dentz <luiz.von.dentz at intel.com>

The Bluetooth spec states that the valid range for SPSM is from
0x0001-0x00ff so it is invalid to accept values outside of this range:

  BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 3, Part A
  page 1059:
  Table 4.15: L2CAP_LE_CREDIT_BASED_CONNECTION_REQ SPSM ranges

CVE: CVE-2022-42896
CC: stable at vger.kernel.org
Reported-by: Tamás Koczka <poprdi at google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz at intel.com>
Reviewed-by: Tedd Ho-Jeong An <tedd.an at intel.com>
CVE-2022-42896
(backported from commit 711f8c3fb3db61897080468586b970c87c61d9e4)
[cengizcan: 4.15 does not have commit 15f02b910562 ("Bluetooth: L2CAP:
Add initial code for Enhanced Credit Based Mode") so skip patching
`l2cap_ecred_conn_req` and only patch `l2cap_le_connect_req` instead.]
[cengizcan: 4.15 does not have L2CAP_CR_LE_BAD_PSM defined so use
L2CAP_CR_BAD_PSM as return value instead since they both indicate same
type of error and are equal.]
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 net/bluetooth/l2cap_core.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 35c04727ddc0..066a16785b92 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -5552,6 +5552,19 @@ static int l2cap_le_connect_req(struct l2cap_conn *conn,
 	BT_DBG("psm 0x%2.2x scid 0x%4.4x mtu %u mps %u", __le16_to_cpu(psm),
 	       scid, mtu, mps);
 
+	/* BLUETOOTH CORE SPECIFICATION Version 5.3 | Vol 3, Part A
+	 * page 1059:
+	 *
+	 * Valid range: 0x0001-0x00ff
+	 *
+	 * Table 4.15: L2CAP_LE_CREDIT_BASED_CONNECTION_REQ SPSM ranges
+	 */
+	if (!psm || __le16_to_cpu(psm) > L2CAP_PSM_LE_DYN_END) {
+		result = L2CAP_CR_BAD_PSM;
+		chan = NULL;
+		goto response;
+	}
+
 	/* Check if we have socket listening on psm */
 	pchan = l2cap_global_chan_by_psm(BT_LISTEN, psm, &conn->hcon->src,
 					 &conn->hcon->dst, LE_LINK);
-- 
2.37.2