netdev - [PATCH v4 net-next 01/13] net: annotate data-races around dev->name_assign

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Date: Tue, 13 Feb 2024 06:32:33 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v4 net-next 01/13] net: annotate data-races around dev->name_assign_type

name_assign_type_show() runs locklessly, we should annotate
accesses to dev->name_assign_type.

Alternative would be to grab devnet_rename_sem semaphore
from name_assign_type_show(), but this would not bring
more accuracy.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/dev.c       | 6 +++---
 net/core/net-sysfs.c | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 7cf15d2bf78def778c397416bfe730434c3cc093..693e08f3304d1de18f859ff4a65947b4a5cb9e4a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1220,13 +1220,13 @@ int dev_change_name(struct net_device *dev, const char *newname)
 			    dev->flags & IFF_UP ? " (while UP)" : "");
 
 	old_assign_type = dev->name_assign_type;
-	dev->name_assign_type = NET_NAME_RENAMED;
+	WRITE_ONCE(dev->name_assign_type, NET_NAME_RENAMED);
 
 rollback:
 	ret = device_rename(&dev->dev, dev->name);
 	if (ret) {
 		memcpy(dev->name, oldname, IFNAMSIZ);
-		dev->name_assign_type = old_assign_type;
+		WRITE_ONCE(dev->name_assign_type, old_assign_type);
 		up_write(&devnet_rename_sem);
 		return ret;
 	}
@@ -1255,7 +1255,7 @@ int dev_change_name(struct net_device *dev, const char *newname)
 			down_write(&devnet_rename_sem);
 			memcpy(dev->name, oldname, IFNAMSIZ);
 			memcpy(oldname, newname, IFNAMSIZ);
-			dev->name_assign_type = old_assign_type;
+			WRITE_ONCE(dev->name_assign_type, old_assign_type);
 			old_assign_type = NET_NAME_RENAMED;
 			goto rollback;
 		} else {
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index a09d507c5b03d24a829bf7af0b7cf1e6a0bdb65a..f4c2b82674951bbeefd880ca22c54e6a32c9f988 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -125,7 +125,7 @@ static DEVICE_ATTR_RO(iflink);
 
 static ssize_t format_name_assign_type(const struct net_device *dev, char *buf)
 {
-	return sysfs_emit(buf, fmt_dec, dev->name_assign_type);
+	return sysfs_emit(buf, fmt_dec, READ_ONCE(dev->name_assign_type));
 }
 
 static ssize_t name_assign_type_show(struct device *dev,
@@ -135,7 +135,7 @@ static ssize_t name_assign_type_show(struct device *dev,
 	struct net_device *ndev = to_net_dev(dev);
 	ssize_t ret = -EINVAL;
 
-	if (ndev->name_assign_type != NET_NAME_UNKNOWN)
+	if (READ_ONCE(ndev->name_assign_type) != NET_NAME_UNKNOWN)
 		ret = netdev_show(dev, attr, buf, format_name_assign_type);
 
 	return ret;
-- 
2.43.0.687.g38aa6559b0-goog