[PATCH 5.15 15/17] Bluetooth: L2CAP: Fix u8 overflow

Greg Kroah-Hartman
2022-12-19T19:27:12Z

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

[ Upstream commit bcd70260ef56e0aee8a4fc6cd214a419900b0765 ]

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 ........@.....
> 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 ........@.......
> 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 ........@.......
= 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 ........@...

Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 761efd7da514..e15fcf72a342 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;
--
2.35.1