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wifi: wext: Limit notifier event flushes to the device's netns

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With mlx5 netdev instance locking enabled, registering an IPoIB netdev
calls the WEXT notifier while holding the instance mutex. Its call to
wireless_nlevent_flush() takes net_rwsem to walk every namespace,
completing the following lockdep dependency cycle:

  netdev instance mutex -> net_rwsem (read) -> GID table mutex
    -> event_handler_rwsem (read) -> netdev instance mutex

RoCE GID enumeration takes the GID table mutex under net_rwsem. GID
updates dispatch events under the table mutex, taking event_handler_rwsem.
The IPoIB event handler takes the netdev instance mutex in
ipoib_queue_work() to traverse child interfaces.

The all-namespace walk originated in the single global worker servicing
per-namespace WEXT queues. The ordering fixes later reused that routine
in netdevice notifiers to prevent delayed WEXT RTM_NEWLINK messages from
following RTM_DELLINK or reporting stale interface flags. A notifier only
needs to drain the affected device's namespace; there is no reason for it
to walk and flush all namespaces.

Pass dev_net(dev) from both notifier callers and make the flush helper
operate on that namespace. Keep the all-namespace walk and net_rwsem in
the existing worker. This removes the instance-mutex -> net_rwsem
dependency while retaining synchronous flushing from the notifiers.

It may seem strange that the fix for a lock cycle across multiple
subsystems lies in a completely unrelated part of the code, but this
seemed the most justified lock cycle edge to break.

Fixes: 8f7b00307b ("net/mlx5e: Convert mlx5 netdevs to instance locking")
Signed-off-by: Cosmin Ratiu <cratiu@nvidia.com>
Link: https://patch.msgid.link/20261021144111.611840-1-cratiu@nvidia.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Cosmin Ratiu 2026-10-21 17:41:11 +03:00 committed by Johannes Berg
parent 7ed5dce55f
commit 48c0045366
3 changed files with 23 additions and 20 deletions
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8
include/net/iw_handler.h
View File

@ -201,6 +201,8 @@
#include <linux/wireless.h> /* IOCTL user space API */
#include <linux/if_ether.h>
struct net;
/***************************** VERSION *****************************/
/*
* This constant is used to know which version of the driver API is
@ -411,10 +413,10 @@ struct iw_spy_data {
void wireless_send_event(struct net_device *dev, unsigned int cmd,
union iwreq_data *wrqu, const char *extra);
#ifdef CONFIG_WEXT_CORE
/* flush all previous wext events - if work is done from netdev notifiers */
void wireless_nlevent_flush(void);
/* Flush previous wext events in this netns from netdev notifiers. */
void wireless_nlevent_flush(struct net *net);
#else
static inline void wireless_nlevent_flush(void) {}
static inline void wireless_nlevent_flush(struct net *net) {}
#endif
/* We may need a function to send a stream of events to user space.

2
net/wireless/core.c
View File

@ -1878,7 +1878,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
return NOTIFY_DONE;
}
wireless_nlevent_flush();
wireless_nlevent_flush(dev_net(dev));
return NOTIFY_OK;
}

33
net/wireless/wext-core.c
View File

@ -342,32 +342,28 @@ static const int compat_event_type_size[] = {
/* IW event code */
void wireless_nlevent_flush(void)
void wireless_nlevent_flush(struct net *net)
{
struct sk_buff *skb;
struct net *net;
down_read(&net_rwsem);
for_each_net(net) {
while ((skb = skb_dequeue(&net->wext_nlevents)))
rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL,
GFP_KERNEL);
}
up_read(&net_rwsem);
while ((skb = skb_dequeue(&net->wext_nlevents)))
rtnl_notify(skb, net, 0, RTNLGRP_LINK, NULL, GFP_KERNEL);
}
EXPORT_SYMBOL_GPL(wireless_nlevent_flush);
static int wext_netdev_notifier_call(struct notifier_block *nb,
unsigned long state, void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
/*
* When a netdev changes state in any way, flush all pending messages
* to avoid them going out in a strange order, e.g. RTM_NEWLINK after
* RTM_DELLINK, or with IFF_UP after without IFF_UP during dev_close()
* or similar - all of which could otherwise happen due to delays from
* schedule_work().
* When a netdev changes state in any way, flush all pending messages in
* its network namespace to avoid them going out in a strange order,
* e.g. RTM_NEWLINK after RTM_DELLINK, or with IFF_UP after without
* IFF_UP during dev_close() or similar - all of which could otherwise
* happen due to delays from schedule_work().
*/
wireless_nlevent_flush();
wireless_nlevent_flush(dev_net(dev));
return NOTIFY_OK;
}
@ -410,7 +406,12 @@ subsys_initcall(wireless_nlevent_init);
/* Process events generated by the wireless layer or the driver. */
static void wireless_nlevent_process(struct work_struct *work)
{
wireless_nlevent_flush();
struct net *net;
down_read(&net_rwsem);
for_each_net(net)
wireless_nlevent_flush(net);
up_read(&net_rwsem);
}
static DECLARE_WORK(wireless_nlevent_work, wireless_nlevent_process);