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: 2ca546b ("IB/sa: Route SA pathrecord query through netlink")
Signed-off-by: Vlad Dumitrescu <vdumitrescu@nvidia.com>
Reviewed-by: Mark Zhang <markzhang@nvidia.com>
Signed-off-by: Edward Srouji <edwards@nvidia.com>
Link: https://patch.msgid.link/20250916163112.98414-1-edwards@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Author: vladum

drivers/infiniband/core/sa_query.c

@@ -1074,14 +1074,15 @@ int ib_nl_handle_set_timeout(struct sk_buff *skb,
 	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;
 	else
 		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)
@@ -1099,9 +1100,10 @@ int ib_nl_handle_set_timeout(struct sk_buff *skb,
 		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;
 }