Null pointer dereference

In the Linux kernel, the following vulnerability has been resolved:

SUNRPC: Fix null pointer dereference in svc_rqst_free()

When alloc_pages_node() returns null in svc_rqst_alloc(), the
null rq_scratch_page pointer will be dereferenced when calling
put_page() in svc_rqst_free(). Fix it by adding a null check.

Addresses-Coverity: (“Dereference after null check”)