netdev - [PATCH net-next] net: ethtool: fix compat with old RSS context API

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Message-ID: <20240702164157.4018425-1-kuba@kernel.org>
Date: Tue,  2 Jul 2024 09:41:57 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	Jakub Kicinski <kuba@...nel.org>,
	przemyslaw.kitszel@...el.com,
	andrew@...n.ch,
	ecree.xilinx@...il.com,
	ahmed.zaki@...el.com
Subject: [PATCH net-next] net: ethtool: fix compat with old RSS context API

Device driver gets access to rxfh_dev, while rxfh is just a local
copy of user space params. We need to check what RSS context ID
driver assigned in rxfh_dev, not rxfh.

Using rxfh leads to trying to store all contexts at index 0xffffffff.
>From the user perspective it leads to "driver chose duplicate ID"
warnings when second context is added and inability to access any
contexts even tho they were successfully created - xa_load() for
the actual context ID will return NULL, and syscall will return -ENOENT.

Looks like a rebasing mistake, since rxfh_dev was added relatively
recently by fb6e30a72539 ("net: ethtool: pass a pointer to parameters
to get/set_rxfh ethtool ops").

Fixes: eac9122f0c41 ("net: ethtool: record custom RSS contexts in the XArray")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: przemyslaw.kitszel@...el.com
CC: andrew@...n.ch
CC: ecree.xilinx@...il.com
CC: ahmed.zaki@...el.com
---
 net/ethtool/ioctl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index d8795ed07ba3..46f0497ae6bc 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1483,13 +1483,13 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	/* Update rss_ctx tracking */
 	if (create && !ops->create_rxfh_context) {
 		/* driver uses old API, it chose context ID */
-		if (WARN_ON(xa_load(&dev->ethtool->rss_ctx, rxfh.rss_context))) {
+		if (WARN_ON(xa_load(&dev->ethtool->rss_ctx, rxfh_dev.rss_context))) {
 			/* context ID reused, our tracking is screwed */
 			kfree(ctx);
 			goto out;
 		}
 		/* Allocate the exact ID the driver gave us */
-		if (xa_is_err(xa_store(&dev->ethtool->rss_ctx, rxfh.rss_context,
+		if (xa_is_err(xa_store(&dev->ethtool->rss_ctx, rxfh_dev.rss_context,
 				       ctx, GFP_KERNEL))) {
 			kfree(ctx);
 			goto out;
-- 
2.45.2