netdev - [PATCH net-next v2 3/4] net-sysfs: prevent uncleared queues from being re-added

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250204170314.146022-4-atenart@kernel.org>
Date: Tue,  4 Feb 2025 18:03:12 +0100
From: Antoine Tenart <atenart@...nel.org>
To: davem@...emloft.net,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com
Cc: Antoine Tenart <atenart@...nel.org>,
	stephen@...workplumber.org,
	gregkh@...uxfoundation.org,
	maxime.chevallier@...tlin.com,
	christophe.leroy@...roup.eu,
	netdev@...r.kernel.org
Subject: [PATCH net-next v2 3/4] net-sysfs: prevent uncleared queues from being re-added

With the (upcoming) removal of the rtnl_trylock/restart_syscall logic
and because of how Tx/Rx queues are implemented (and their
requirements), it might happen that a queue is re-added before having
the chance to be cleared. In such rare case, do not complete the queue
addition operation.

Signed-off-by: Antoine Tenart <atenart@...nel.org>
---
 net/core/net-sysfs.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 0b7ee260613d..027af27517fa 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1210,6 +1210,22 @@ static int rx_queue_add_kobject(struct net_device *dev, int index)
 	struct kobject *kobj = &queue->kobj;
 	int error = 0;
 
+	/* Rx queues are cleared in rx_queue_release to allow later
+	 * re-registration. This is triggered when their kobj refcount is
+	 * dropped.
+	 *
+	 * If a queue is removed while both a read (or write) operation and a
+	 * the re-addition of the same queue are pending (waiting on rntl_lock)
+	 * it might happen that the re-addition will execute before the read,
+	 * making the initial removal to never happen (queue's kobj refcount
+	 * won't drop enough because of the pending read). In such rare case,
+	 * return to allow the removal operation to complete.
+	 */
+	if (unlikely(kobj->state_initialized)) {
+		netdev_warn_once(dev, "Cannot re-add rx queues before their removal completed");
+		return -EAGAIN;
+	}
+
 	/* Kobject_put later will trigger rx_queue_release call which
 	 * decreases dev refcount: Take that reference here
 	 */
@@ -1898,6 +1914,22 @@ static int netdev_queue_add_kobject(struct net_device *dev, int index)
 	struct kobject *kobj = &queue->kobj;
 	int error = 0;
 
+	/* Tx queues are cleared in netdev_queue_release to allow later
+	 * re-registration. This is triggered when their kobj refcount is
+	 * dropped.
+	 *
+	 * If a queue is removed while both a read (or write) operation and a
+	 * the re-addition of the same queue are pending (waiting on rntl_lock)
+	 * it might happen that the re-addition will execute before the read,
+	 * making the initial removal to never happen (queue's kobj refcount
+	 * won't drop enough because of the pending read). In such rare case,
+	 * return to allow the removal operation to complete.
+	 */
+	if (unlikely(kobj->state_initialized)) {
+		netdev_warn_once(dev, "Cannot re-add tx queues before their removal completed");
+		return -EAGAIN;
+	}
+
 	/* Kobject_put later will trigger netdev_queue_release call
 	 * which decreases dev refcount: Take that reference here
 	 */
-- 
2.48.1