IB/sa: Fix sa_local_svc_timeout_ms read race

When computing the delta, the sa_local_svc_timeout_ms is read without
ib_nl_request_lock held. Though unlikely in practice, this can cause
a race condition if multiple local service threads are managing the
timeout.

Fixes: 2ca546b92a02 ("IB/sa: Route SA pathrecord query through netlink")
Signed-off-by: Vlad Dumitrescu <[e-mail]>
Reviewed-by: Mark Zhang <[e-mail]>
Signed-off-by: Edward Srouji <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Leon Romanovsky <[e-mail]>

drivers/infiniband/core/sa_query.c

···
 	if (timeout > IB_SA_LOCAL_SVC_TIMEOUT_MAX)
 		timeout = IB_SA_LOCAL_SVC_TIMEOUT_MAX;
 
+	spin_lock_irqsave(&ib_nl_request_lock, flags);
+
 	delta = timeout - sa_local_svc_timeout_ms;
 	if (delta < 0)
 		abs_delta = -delta;
···
 		abs_delta = delta;
 
 	if (delta != 0) {
-		spin_lock_irqsave(&ib_nl_request_lock, flags);
 		sa_local_svc_timeout_ms = timeout;
 		list_for_each_entry(query, &ib_nl_request_list, list) {
 			if (delta < 0 && abs_delta > query->timeout)
···
 		if (delay)
 			mod_delayed_work(ib_nl_wq, &ib_nl_timed_work,
 					 (unsigned long)delay);
-		spin_unlock_irqrestore(&ib_nl_request_lock, flags);
 	}
+
+	spin_unlock_irqrestore(&ib_nl_request_lock, flags);
 
 settimeout_out:
 	return 0;