CVE-2023-54274 RDMA/srpt: Add a check for valid 'mad_agent' pointer

In the Linux kernel, the following vulnerability has been resolved: RDMA/srpt: Add a check for valid 'madagent' pointer When unregistering MAD agent, srpt module has a non-null check for 'madagent' pointer before invoking ibunregistermadagent. This check can pass if 'madagent' variable holds an...