[SRU OEM-6.0 1/1] Bluetooth: L2CAP: Fix u8 overflow

[Cengiz Can]

From: Sungwoo Kim <iam at sung-woo.kim>

By keep sending L2CAP_CONF_REQ packets, chan->num_conf_rsp increases
multiple times and eventually it will wrap around the maximum number
(i.e., 255).
This patch prevents this by adding a boundary check with
L2CAP_MAX_CONF_RSP

Btmon log:
Bluetooth monitor ver 5.64
= Note: Linux version 6.1.0-rc2 (x86_64)                               0.264594
= Note: Bluetooth subsystem version 2.22                               0.264636
@ MGMT Open: btmon (privileged) version 1.22                  {0x0001} 0.272191
= New Index: 00:00:00:00:00:00 (Primary,Virtual,hci0)          [hci0] 13.877604
@ RAW Open: 9496 (privileged) version 2.22                   {0x0002} 13.890741
= Open Index: 00:00:00:00:00:00                                [hci0] 13.900426
(...)
> ACL Data RX: Handle 200 flags 0x00 dlen 1033             #32 [hci0] 14.273106
        invalid packet size (12 != 1033)
        08 00 01 00 02 01 04 00 01 10 ff ff              ............
> ACL Data RX: Handle 200 flags 0x00 dlen 1547             #33 [hci0] 14.273561
        invalid packet size (14 != 1547)
        0a 00 01 00 04 01 06 00 40 00 00 00 00 00        ........ at .....
> ACL Data RX: Handle 200 flags 0x00 dlen 2061             #34 [hci0] 14.274390
        invalid packet size (16 != 2061)
        0c 00 01 00 04 01 08 00 40 00 00 00 00 00 00 04  ........ at .......
> ACL Data RX: Handle 200 flags 0x00 dlen 2061             #35 [hci0] 14.274932
        invalid packet size (16 != 2061)
        0c 00 01 00 04 01 08 00 40 00 00 00 07 00 03 00  ........ at .......
= bluetoothd: Bluetooth daemon 5.43                                   14.401828
> ACL Data RX: Handle 200 flags 0x00 dlen 1033             #36 [hci0] 14.275753
        invalid packet size (12 != 1033)
        08 00 01 00 04 01 04 00 40 00 00 00              ........ at ...

Signed-off-by: Sungwoo Kim <iam at sung-woo.kim>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz at intel.com>
CVE-2022-45934
(cherry picked from commit bcd70260ef56e0aee8a4fc6cd214a419900b0765)
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 net/bluetooth/l2cap_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 4df3d0ed6c80..6402edcacdcb 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4453,7 +4453,8 @@ static inline int l2cap_config_req(struct l2cap_conn *conn,
 
 	chan->ident = cmd->ident;
 	l2cap_send_cmd(conn, cmd->ident, L2CAP_CONF_RSP, len, rsp);
-	chan->num_conf_rsp++;
+	if (chan->num_conf_rsp < L2CAP_CONF_MAX_CONF_RSP)
+		chan->num_conf_rsp++;
 
 	/* Reset config buffer. */
 	chan->conf_len = 0;
-- 
2.37.2