mxser: fix xmit_buf leak in activate when LSR == 0xff
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.33 by commit b125b08dbee3611f03f53b71471813ed4ccafcdd, it was introduced in version v2.6.33 by commit 6769140d304731f0a3b177470a2adb4bacd9036b. For more details please see the references link.