Re: KASAN: use-after-free in __mutex_lock

Sungwoo Kim
2022-09-30T16:09:50Z

Hi Dentz,
How about to use l2cap_get_chan_by_scid because it looks resposible to
handle ref_cnt.

Signed-off-by: Sungwoo Kim <iam@sung-woo.kim>
---
net/bluetooth/l2cap_core.c | 24 +++++++-----------------
1 file changed, 7 insertions(+), 17 deletions(-)

diff --git a/net/bluetooth/l2cap_core.c b/net/bluetooth/l2cap_core.c
index 2c9de67da..d3a074cbc 100644
--- a/net/bluetooth/l2cap_core.c
+++ b/net/bluetooth/l2cap_core.c
@@ -4291,26 +4291,18 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
BT_DBG("dcid 0x%4.4x scid 0x%4.4x result 0x%2.2x status 0x%2.2x",
dcid, scid, result, status);

- mutex_lock(&conn->chan_lock);
-
if (scid) {
- chan = __l2cap_get_chan_by_scid(conn, scid);
- if (!chan) {
- err = -EBADSLT;
- goto unlock;
- }
+ chan = l2cap_get_chan_by_scid(conn, scid);
+ if (!chan)
+ return -EBADSLT;
} else {
- chan = __l2cap_get_chan_by_ident(conn, cmd->ident);
- if (!chan) {
- err = -EBADSLT;
- goto unlock;
- }
+ chan = l2cap_get_chan_by_ident(conn, cmd->ident);
+ if (!chan)
+ return -EBADSLT;
}

err = 0;

- l2cap_chan_lock(chan);
-
switch (result) {
case L2CAP_CR_SUCCESS:
l2cap_state_change(chan, BT_CONFIG);
@@ -4336,9 +4328,7 @@ static int l2cap_connect_create_rsp(struct l2cap_conn *conn,
}

l2cap_chan_unlock(chan);
-
-unlock:
- mutex_unlock(&conn->chan_lock);
+ l2cap_chan_put(chan);

return err;
}
--
2.25.1