Bluetooth: L2CAP: Fix attempting to access uninitialized memory

stable inclusion
from stable-v5.10.154
commit 26ca2ac091b49281d73df86111d16e5a76e43bd7
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I5ZNRS
CVE: CVE-2022-42895

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=26ca2ac091b49281d73df86111d16e5a76e43bd7

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

commit b1a2cd50 upstream.

On l2cap_parse_conf_req the variable efs is only initialized if
remote_efs has been set.

CVE: CVE-2022-42895
CC: stable@vger.kernel.org
Reported-by: NTamás Koczka <poprdi@google.com>
Signed-off-by: NLuiz Augusto von Dentz <luiz.von.dentz@intel.com>
Reviewed-by: NTedd Ho-Jeong An <tedd.an@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NBaisong Zhong <zhongbaisong@huawei.com>
Reviewed-by: NLiu Jian <liujian56@huawei.com>
Reviewed-by: NYue Haibing <yuehaibing@huawei.com>
Reviewed-by: NWang Weiyang <wangweiyang2@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

net/bluetooth/l2cap_core.c

@@ -3758,7 +3758,8 @@ static int l2cap_parse_conf_req(struct l2cap_chan *chan, void *data, size_t data
 			l2cap_add_conf_opt(&ptr, L2CAP_CONF_RFC,
 					   sizeof(rfc), (unsigned long) &rfc, endptr - ptr);
 
-			if (test_bit(FLAG_EFS_ENABLE, &chan->flags)) {
+			if (remote_efs &&
+			    test_bit(FLAG_EFS_ENABLE, &chan->flags)) {
 				chan->remote_id = efs.id;
 				chan->remote_stype = efs.stype;
 				chan->remote_msdu = le16_to_cpu(efs.msdu);