From: Abhishek Pandit-Subedi <abhishekpan...@chromium.org>
[ Upstream commit 20ae4089d0afeb24e9ceb026b996bfa55c983cc2 ]
Since l2cap_sock_teardown_cb doesn't acquire the channel lock before
setting the socket as zapped, it could potentially race with
l2cap_sock_release which frees the socket. Thus, wait until the cleanup
is complete before marking the socket as zapped.
This race was reproduced on a JBL GO speaker after the remote device
rejected L2CAP connection due to resource unavailability.
Here is a dmesg log with debug logs from a repro of this bug:
[ 3465.424086] Bluetooth: hci_core.c:hci_acldata_packet() hci0 len 16 handle
0x0003 flags 0x0002
[ 3465.424090] Bluetooth: hci_conn.c:hci_conn_enter_active_mode() hcon
00000000cfedd07d mode 0
[ 3465.424094] Bluetooth: l2cap_core.c:l2cap_recv_acldata() conn
000000007eae8952 len 16 flags 0x2
[ 3465.424098] Bluetooth: l2cap_core.c:l2cap_recv_frame() len 12, cid 0x0001
[ 3465.424102] Bluetooth: l2cap_core.c:l2cap_raw_recv() conn 000000007eae8952
[ 3465.424175] Bluetooth: l2cap_core.c:l2cap_sig_channel() code 0x03 len 8 id
0x0c
[ 3465.424180] Bluetooth: l2cap_core.c:l2cap_connect_create_rsp() dcid 0x0045
scid 0x0000 result 0x02 status 0x00
[ 3465.424189] Bluetooth: l2cap_core.c:l2cap_chan_put() chan 000000006acf9bff
orig refcnt 4
[ 3465.424196] Bluetooth: l2cap_core.c:l2cap_chan_del() chan 000000006acf9bff,
conn 000000007eae8952, err 111, state BT_CONNECT
[ 3465.424203] Bluetooth: l2cap_sock.c:l2cap_sock_teardown_cb() chan
000000006acf9bff state BT_CONNECT
[ 3465.424221] Bluetooth: l2cap_core.c:l2cap_chan_put() chan 000000006acf9bff
orig refcnt 3
[ 3465.424226] Bluetooth: hci_core.h:hci_conn_drop() hcon 00000000cfedd07d orig
refcnt 6
[ 3465.424234] BUG: spinlock bad magic on CPU#2, kworker/u17:0/159
[ 3465.425626] Bluetooth: hci_sock.c:hci_sock_sendmsg() sock 000000002bb0cb64
sk 00000000a7964053
[ 3465.430330] lock: 0xffffff804410aac0, .magic: 00000000, .owner: <none>/-1,
.owner_cpu: 0
[ 3465.430332] Causing a watchdog bite!
Signed-off-by: Abhishek Pandit-Subedi <abhishekpan...@chromium.org>
Reported-by: Balakrishna Godavarthi <bgoda...@codeaurora.org>
Reviewed-by: Manish Mandlik <mmand...@chromium.org>
Signed-off-by: Marcel Holtmann <mar...@holtmann.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
net/bluetooth/l2cap_sock.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index e1a3e66b17540..e7cfe28140c39 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -1521,8 +1521,6 @@ static void l2cap_sock_teardown_cb(struct l2cap_chan
*chan, int err)
parent = bt_sk(sk)->parent;
- sock_set_flag(sk, SOCK_ZAPPED);
-
switch (chan->state) {
case BT_OPEN:
case BT_BOUND:
@@ -1549,8 +1547,11 @@ static void l2cap_sock_teardown_cb(struct l2cap_chan
*chan, int err)
break;
}
-
release_sock(sk);
+
+ /* Only zap after cleanup to avoid use after free race */
+ sock_set_flag(sk, SOCK_ZAPPED);
+
}
static void l2cap_sock_state_change_cb(struct l2cap_chan *chan, int state,
--
2.25.1
