Add missing chan lock in l2cap_ecred_reconf_rsp

Summary

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: l2cap: Add missing chan lock in l2cap_ecred_reconf_rsp l2cap_ecred_reconf_rsp() calls l2cap_chan_del() without holding l2cap_chan_lock(). Every other l2cap_chan_del() caller in the file acquires the lock first. A remote BLE device can send a crafted L2CAP ECRED reconfiguration response to corrupt the channel list while another thread is iterating it. Add l2cap_chan_hold() and l2cap_chan_lock() before l2cap_chan_del(), and l2cap_chan_unlock() and l2cap_chan_put() after, matching the pattern used in l2cap_ecred_conn_rsp() and l2cap_conn_del(). A flaw was found in the Linux kernel's Bluetooth Logical Link Control and Adaptation Protocol (L2CAP) implementation. A remote Bluetooth Low Energy (BLE) device can exploit this by sending a specially crafted L2CAP ECRED reconfiguration response. This can lead to the corruption of the channel list, potentially causing a Denial of Service (DoS) by making the system unstable or unresponsive. The vulnerability is due to a missing channel lock when a channel is deleted. Red Hat severity: Important — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H). Weakness: CWE-414. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.