Bluetooth: L2CAP: Fix l2cap_global_chan_by_psm regression

stable inclusion
from stable-v4.19.256
commit a55ac4419fb75295386e9cd386ab34b62b18e869
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I64WCC


CVE: CVE-2022-20566

--------------------------------

commit 332f1795 upstream.

The patch d0be8347: "Bluetooth: L2CAP: Fix use-after-free caused
by l2cap_chan_put" from Jul 21, 2022, leads to the following Smatch
static checker warning:

        net/bluetooth/l2cap_core.c:1977 l2cap_global_chan_by_psm()
        error: we previously assumed 'c' could be null (see line 1996)

Fixes: d0be8347 ("Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lu Jialin <lujialin4@huawei.com>
Reviewed-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Wang Weiyang <wangweiyang2@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>