RDMA/srpt: Support specifying the srpt_service_guid parameter

Make loading ib_srpt with this parameter set work. The current behavior is
that setting that parameter while loading the ib_srpt kernel module
triggers the following kernel crash:

BUG: kernel NULL pointer dereference, address: 0000000000000000
Call Trace:
 <TASK>
 parse_one+0x18c/0x1d0
 parse_args+0xe1/0x230
 load_module+0x8de/0xa60
 init_module_from_file+0x8b/0xd0
 idempotent_init_module+0x181/0x240
 __x64_sys_finit_module+0x5a/0xb0
 do_syscall_64+0x5f/0xe0
 entry_SYSCALL_64_after_hwframe+0x6e/0x76

Cc: LiHonggang <[email protected]>
Reported-by: LiHonggang <[email protected]>
Fixes: a42d985 ("ib_srpt: Initial SRP Target merge for v3.3-rc1")
Signed-off-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Leon Romanovsky <[email protected]>

Author: bvanassche

drivers/infiniband/ulp/srpt/ib_srpt.c

@@ -79,12 +79,16 @@ module_param(srpt_srq_size, int, 0444);
 MODULE_PARM_DESC(srpt_srq_size,
 		 "Shared receive queue (SRQ) size.");
 
+static int srpt_set_u64_x(const char *buffer, const struct kernel_param *kp)
+{
+	return kstrtou64(buffer, 16, (u64 *)kp->arg);
+}
 static int srpt_get_u64_x(char *buffer, const struct kernel_param *kp)
 {
 	return sprintf(buffer, "0x%016llx\n", *(u64 *)kp->arg);
 }
-module_param_call(srpt_service_guid, NULL, srpt_get_u64_x, &srpt_service_guid,
-		  0444);
+module_param_call(srpt_service_guid, srpt_set_u64_x, srpt_get_u64_x,
+		  &srpt_service_guid, 0444);
 MODULE_PARM_DESC(srpt_service_guid,
 		 "Using this value for ioc_guid, id_ext, and cm_listen_id instead of using the node_guid of the first HCA.");