Patch "net: ethtool: add a mutex protecting RSS contexts" has been added to the 6.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: ethtool: add a mutex protecting RSS contexts

to the 6.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-ethtool-add-a-mutex-protecting-rss-contexts.patch
and it can be found in the queue-6.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 01764eaa588997eb987eb407719bfc56bdf3907c
Author: Edward Cree <ecree.xilinx@xxxxxxxxx>
Date:   Thu Jun 27 16:33:51 2024 +0100

    net: ethtool: add a mutex protecting RSS contexts
    
    [ Upstream commit 87925151191b64d9623e63ccf11e517eacc99d7d ]
    
    While this is not needed to serialise the ethtool entry points (which
     are all under RTNL), drivers may have cause to asynchronously access
     dev->ethtool->rss_ctx; taking dev->ethtool->rss_lock allows them to
     do this safely without needing to take the RTNL.
    
    Signed-off-by: Edward Cree <ecree.xilinx@xxxxxxxxx>
    Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>
    Link: https://patch.msgid.link/7f9c15eb7525bf87af62c275dde3a8570ee8bf0a.1719502240.git.ecree.xilinx@xxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Stable-dep-of: 7195f0ef7f5b ("ethtool: fix setting key and resetting indir at once")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 8fa2f8bd474b6..787dd63c3acb3 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -1055,10 +1055,13 @@ int ethtool_virtdev_set_link_ksettings(struct net_device *dev,
 /**
  * struct ethtool_netdev_state - per-netdevice state for ethtool features
  * @rss_ctx:		XArray of custom RSS contexts
+ * @rss_lock:		Protects entries in @rss_ctx.  May be taken from
+ *			within RTNL.
  * @wol_enabled:	Wake-on-LAN is enabled
  */
 struct ethtool_netdev_state {
 	struct xarray		rss_ctx;
+	struct mutex		rss_lock;
 	unsigned		wol_enabled:1;
 };
 
diff --git a/net/core/dev.c b/net/core/dev.c
index b390b4cd9098f..8a9ab7b12c618 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -10287,6 +10287,7 @@ int register_netdevice(struct net_device *dev)
 
 	/* rss ctx ID 0 is reserved for the default context, start from 1 */
 	xa_init_flags(&dev->ethtool->rss_ctx, XA_FLAGS_ALLOC1);
+	mutex_init(&dev->ethtool->rss_lock);
 
 	spin_lock_init(&dev->addr_list_lock);
 	netdev_set_addr_lockdep_class(dev);
@@ -11142,6 +11143,7 @@ static void netdev_rss_contexts_free(struct net_device *dev)
 	struct ethtool_rxfh_context *ctx;
 	unsigned long context;
 
+	mutex_lock(&dev->ethtool->rss_lock);
 	xa_for_each(&dev->ethtool->rss_ctx, context, ctx) {
 		struct ethtool_rxfh_param rxfh;
 
@@ -11157,6 +11159,7 @@ static void netdev_rss_contexts_free(struct net_device *dev)
 		kfree(ctx);
 	}
 	xa_destroy(&dev->ethtool->rss_ctx);
+	mutex_unlock(&dev->ethtool->rss_lock);
 }
 
 /**
@@ -11269,6 +11272,8 @@ void unregister_netdevice_many_notify(struct list_head *head,
 		if (dev->netdev_ops->ndo_uninit)
 			dev->netdev_ops->ndo_uninit(dev);
 
+		mutex_destroy(&dev->ethtool->rss_lock);
+
 		if (skb)
 			rtmsg_ifinfo_send(skb, dev, GFP_KERNEL, portid, nlh);
 
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index 1e87131f2caf4..d9c8a6a16cb2a 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -1285,6 +1285,7 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	struct netlink_ext_ack *extack = NULL;
 	struct ethtool_rxnfc rx_rings;
 	struct ethtool_rxfh rxfh;
+	bool locked = false; /* dev->ethtool->rss_lock taken */
 	u32 indir_bytes = 0;
 	bool create = false;
 	u8 *rss_config;
@@ -1381,6 +1382,10 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 		}
 	}
 
+	if (rxfh.rss_context) {
+		mutex_lock(&dev->ethtool->rss_lock);
+		locked = true;
+	}
 	if (create) {
 		if (rxfh_dev.rss_delete) {
 			ret = -EINVAL;
@@ -1471,6 +1476,8 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	}
 
 out:
+	if (locked)
+		mutex_unlock(&dev->ethtool->rss_lock);
 	kfree(rss_config);
 	return ret;
 }