From: Antoine Tenart atenart@kernel.org
[ Upstream commit 7e54f85c60828842be27e0149f3533357225090e ]
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@kernel.org Link: https://patch.msgid.link/20250204170314.146022-4-atenart@kernel.org Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.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 b398a2e0c243d..d6d0c3082b82b 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -1100,6 +1100,22 @@ 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 */ @@ -1811,6 +1827,22 @@ 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 */