CVE-2022-48816 SUNRPC: lock against ->sock changing during sysfs read

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: lock against -sock changing during sysfs read -sock can be set to NULL asynchronously unless -recvmutex is held. So it is important to hold that mutex. Otherwise a sysfs read can trigger an oops. Commit 17f09d3f619a...