[PATCH net 03/12] net: shaper: fix trivial ordering issue in net_shaper_commit()

[Jakub Kicinski <kuba@kernel.org>]

We should update the entry before we mark it as valid.

Fixes: 93954b40f6a4 ("net-shapers: implement NL set and delete operations")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/shaper/shaper.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/shaper/shaper.c b/net/shaper/shaper.c
index c5cf10543af0..692e38df42cb 100644
--- a/net/shaper/shaper.c
+++ b/net/shaper/shaper.c
@@ -295,6 +295,10 @@ net_shaper_lookup(struct net_shaper_binding *binding,
 				       NET_SHAPER_VALID))
 		return NULL;
 
+	/* Pairs with smp_wmb() in net_shaper_commit(): if the entry is
+	 * valid, its contents must be visible too.
+	 */
+	smp_rmb();
 	return xa_load(&hierarchy->shapers, index);
 }
 
@@ -411,8 +415,9 @@ static void net_shaper_commit(struct net_shaper_binding *binding,
 		/* Successful update: drop the tentative mark
 		 * and update the hierarchy container.
 		 */
-		xa_set_mark(&hierarchy->shapers, index, NET_SHAPER_VALID);
 		*cur = shapers[i];
+		smp_wmb();
+		xa_set_mark(&hierarchy->shapers, index, NET_SHAPER_VALID);
 	}
 }
 
@@ -833,6 +838,10 @@ int net_shaper_nl_get_dumpit(struct sk_buff *skb,
 	for (; (shaper = xa_find(&hierarchy->shapers, &ctx->start_index,
 				 U32_MAX, NET_SHAPER_VALID));
 	     ctx->start_index++) {
+		/* Pairs with smp_wmb() in net_shaper_commit(): the entry
+		 * is marked VALID, so its contents must be visible too.
+		 */
+		smp_rmb();
 		ret = net_shaper_fill_one(skb, binding, shaper, info);
 		if (ret)
 			break;
-- 
2.54.0