[PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Alexander Popov]

Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
the virt_wifi net devices. However, unregistering a virt_wifi device in
netdev_run_todo() can happen together with the device referenced by
SET_NETDEV_DEV().

It can result in use-after-free during the ethtool operations performed
on a virt_wifi device that is currently being unregistered. Such a net
device can have the `dev.parent` field pointing to the freed memory,
but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.

Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:

 ==================================================================
 BUG: KASAN: slab-use-after-free in __pm_runtime_resume+0xe2/0xf0
 Read of size 2 at addr ffff88810cfc46f8 by task pm/606

 Call Trace:
  <TASK>
  dump_stack_lvl+0x4d/0x70
  print_report+0x170/0x4f3
  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
  kasan_report+0xda/0x110
  ? __pm_runtime_resume+0xe2/0xf0
  ? __pm_runtime_resume+0xe2/0xf0
  __pm_runtime_resume+0xe2/0xf0
  ethnl_ops_begin+0x49/0x270
  ethnl_set_features+0x23c/0xab0
  ? __pfx_ethnl_set_features+0x10/0x10
  ? kvm_sched_clock_read+0x11/0x20
  ? local_clock_noinstr+0xf/0xf0
  ? local_clock+0x10/0x30
  ? kasan_save_track+0x25/0x60
  ? __kasan_kmalloc+0x7f/0x90
  ? genl_family_rcv_msg_attrs_parse.isra.0+0x150/0x2c0
  genl_family_rcv_msg_doit+0x1e7/0x2c0
  ? __pfx_genl_family_rcv_msg_doit+0x10/0x10
  ? __pfx_cred_has_capability.isra.0+0x10/0x10
  ? stack_trace_save+0x8e/0xc0
  genl_rcv_msg+0x411/0x660
  ? __pfx_genl_rcv_msg+0x10/0x10
  ? __pfx_ethnl_set_features+0x10/0x10
  netlink_rcv_skb+0x121/0x380
  ? __pfx_genl_rcv_msg+0x10/0x10
  ? __pfx_netlink_rcv_skb+0x10/0x10
  ? __pfx_down_read+0x10/0x10
  genl_rcv+0x23/0x30
  netlink_unicast+0x60f/0x830
  ? __pfx_netlink_unicast+0x10/0x10
  ? __pfx___alloc_skb+0x10/0x10
  netlink_sendmsg+0x6ea/0xbc0
  ? __pfx_netlink_sendmsg+0x10/0x10
  ? __futex_queue+0x10b/0x1f0
  ____sys_sendmsg+0x7a2/0x950
  ? copy_msghdr_from_user+0x26b/0x430
  ? __pfx_____sys_sendmsg+0x10/0x10
  ? __pfx_copy_msghdr_from_user+0x10/0x10
  ___sys_sendmsg+0xf8/0x180
  ? __pfx____sys_sendmsg+0x10/0x10
  ? __pfx_futex_wait+0x10/0x10
  ? fdget+0x2e4/0x4a0
  __sys_sendmsg+0x11f/0x1c0
  ? __pfx___sys_sendmsg+0x10/0x10
  do_syscall_64+0xe2/0x570
  ? exc_page_fault+0x66/0xb0
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  </TASK>

This fix may be combined with another one in the ethtool subsystem:
https://lore.kernel.org/all/20260322075917.254874-1-alex.popov@linux.com/T/#u

Fixes: d43c65b05b848e0b ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Popov <alex.popov@linux.com>
---
 drivers/net/wireless/virtual/virt_wifi.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/wireless/virtual/virt_wifi.c b/drivers/net/wireless/virtual/virt_wifi.c
index 885dc7243e8d..97bd39d89e98 100644
--- a/drivers/net/wireless/virtual/virt_wifi.c
+++ b/drivers/net/wireless/virtual/virt_wifi.c
@@ -557,7 +557,6 @@ static int virt_wifi_newlink(struct net_device *dev,
 	eth_hw_addr_inherit(dev, priv->lowerdev);
 	netif_stacked_transfer_operstate(priv->lowerdev, dev);
 
-	SET_NETDEV_DEV(dev, &priv->lowerdev->dev);
 	dev->ieee80211_ptr = kzalloc_obj(*dev->ieee80211_ptr);
 
 	if (!dev->ieee80211_ptr) {
-- 
2.53.0

Re: [PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Greg KH]

On Wed, Mar 25, 2026 at 01:46:02AM +0300, Alexander Popov wrote:
> Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
> the virt_wifi net devices. However, unregistering a virt_wifi device in
> netdev_run_todo() can happen together with the device referenced by
> SET_NETDEV_DEV().
> 
> It can result in use-after-free during the ethtool operations performed
> on a virt_wifi device that is currently being unregistered. Such a net
> device can have the `dev.parent` field pointing to the freed memory,
> but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.
> 
> Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:
> 
>  ==================================================================
>  BUG: KASAN: slab-use-after-free in __pm_runtime_resume+0xe2/0xf0
>  Read of size 2 at addr ffff88810cfc46f8 by task pm/606
> 
>  Call Trace:
>   <TASK>
>   dump_stack_lvl+0x4d/0x70
>   print_report+0x170/0x4f3
>   ? __pfx__raw_spin_lock_irqsave+0x10/0x10
>   kasan_report+0xda/0x110
>   ? __pm_runtime_resume+0xe2/0xf0
>   ? __pm_runtime_resume+0xe2/0xf0
>   __pm_runtime_resume+0xe2/0xf0
>   ethnl_ops_begin+0x49/0x270
>   ethnl_set_features+0x23c/0xab0
>   ? __pfx_ethnl_set_features+0x10/0x10
>   ? kvm_sched_clock_read+0x11/0x20
>   ? local_clock_noinstr+0xf/0xf0
>   ? local_clock+0x10/0x30
>   ? kasan_save_track+0x25/0x60
>   ? __kasan_kmalloc+0x7f/0x90
>   ? genl_family_rcv_msg_attrs_parse.isra.0+0x150/0x2c0
>   genl_family_rcv_msg_doit+0x1e7/0x2c0
>   ? __pfx_genl_family_rcv_msg_doit+0x10/0x10
>   ? __pfx_cred_has_capability.isra.0+0x10/0x10
>   ? stack_trace_save+0x8e/0xc0
>   genl_rcv_msg+0x411/0x660
>   ? __pfx_genl_rcv_msg+0x10/0x10
>   ? __pfx_ethnl_set_features+0x10/0x10
>   netlink_rcv_skb+0x121/0x380
>   ? __pfx_genl_rcv_msg+0x10/0x10
>   ? __pfx_netlink_rcv_skb+0x10/0x10
>   ? __pfx_down_read+0x10/0x10
>   genl_rcv+0x23/0x30
>   netlink_unicast+0x60f/0x830
>   ? __pfx_netlink_unicast+0x10/0x10
>   ? __pfx___alloc_skb+0x10/0x10
>   netlink_sendmsg+0x6ea/0xbc0
>   ? __pfx_netlink_sendmsg+0x10/0x10
>   ? __futex_queue+0x10b/0x1f0
>   ____sys_sendmsg+0x7a2/0x950
>   ? copy_msghdr_from_user+0x26b/0x430
>   ? __pfx_____sys_sendmsg+0x10/0x10
>   ? __pfx_copy_msghdr_from_user+0x10/0x10
>   ___sys_sendmsg+0xf8/0x180
>   ? __pfx____sys_sendmsg+0x10/0x10
>   ? __pfx_futex_wait+0x10/0x10
>   ? fdget+0x2e4/0x4a0
>   __sys_sendmsg+0x11f/0x1c0
>   ? __pfx___sys_sendmsg+0x10/0x10
>   do_syscall_64+0xe2/0x570
>   ? exc_page_fault+0x66/0xb0
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>   </TASK>
> 
> This fix may be combined with another one in the ethtool subsystem:
> https://lore.kernel.org/all/20260322075917.254874-1-alex.popov@linux.com/T/#u
> 
> Fixes: d43c65b05b848e0b ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexander Popov <alex.popov@linux.com>
> ---
>  drivers/net/wireless/virtual/virt_wifi.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/virtual/virt_wifi.c b/drivers/net/wireless/virtual/virt_wifi.c
> index 885dc7243e8d..97bd39d89e98 100644
> --- a/drivers/net/wireless/virtual/virt_wifi.c
> +++ b/drivers/net/wireless/virtual/virt_wifi.c
> @@ -557,7 +557,6 @@ static int virt_wifi_newlink(struct net_device *dev,
>  	eth_hw_addr_inherit(dev, priv->lowerdev);
>  	netif_stacked_transfer_operstate(priv->lowerdev, dev);
>  
> -	SET_NETDEV_DEV(dev, &priv->lowerdev->dev);
>  	dev->ieee80211_ptr = kzalloc_obj(*dev->ieee80211_ptr);
>  
>  	if (!dev->ieee80211_ptr) {
> -- 
> 2.53.0

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Breno Leitao]

On Wed, Mar 25, 2026 at 01:46:02AM +0300, Alexander Popov wrote:
> Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
> the virt_wifi net devices. However, unregistering a virt_wifi device in
> netdev_run_todo() can happen together with the device referenced by
> SET_NETDEV_DEV().
> 
> It can result in use-after-free during the ethtool operations performed
> on a virt_wifi device that is currently being unregistered. Such a net
> device can have the `dev.parent` field pointing to the freed memory,
> but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.
> 
> Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:
> 
>  ==================================================================
>  BUG: KASAN: slab-use-after-free in __pm_runtime_resume+0xe2/0xf0
>  Read of size 2 at addr ffff88810cfc46f8 by task pm/606
> 
>  Call Trace:
>   <TASK>
>   dump_stack_lvl+0x4d/0x70
>   print_report+0x170/0x4f3
>   ? __pfx__raw_spin_lock_irqsave+0x10/0x10
>   kasan_report+0xda/0x110
>   ? __pm_runtime_resume+0xe2/0xf0
>   ? __pm_runtime_resume+0xe2/0xf0
>   __pm_runtime_resume+0xe2/0xf0
>   ethnl_ops_begin+0x49/0x270
>   ethnl_set_features+0x23c/0xab0
>   ? __pfx_ethnl_set_features+0x10/0x10
>   ? kvm_sched_clock_read+0x11/0x20
>   ? local_clock_noinstr+0xf/0xf0
>   ? local_clock+0x10/0x30
>   ? kasan_save_track+0x25/0x60
>   ? __kasan_kmalloc+0x7f/0x90
>   ? genl_family_rcv_msg_attrs_parse.isra.0+0x150/0x2c0
>   genl_family_rcv_msg_doit+0x1e7/0x2c0
>   ? __pfx_genl_family_rcv_msg_doit+0x10/0x10
>   ? __pfx_cred_has_capability.isra.0+0x10/0x10
>   ? stack_trace_save+0x8e/0xc0
>   genl_rcv_msg+0x411/0x660
>   ? __pfx_genl_rcv_msg+0x10/0x10
>   ? __pfx_ethnl_set_features+0x10/0x10
>   netlink_rcv_skb+0x121/0x380
>   ? __pfx_genl_rcv_msg+0x10/0x10
>   ? __pfx_netlink_rcv_skb+0x10/0x10
>   ? __pfx_down_read+0x10/0x10
>   genl_rcv+0x23/0x30
>   netlink_unicast+0x60f/0x830
>   ? __pfx_netlink_unicast+0x10/0x10
>   ? __pfx___alloc_skb+0x10/0x10
>   netlink_sendmsg+0x6ea/0xbc0
>   ? __pfx_netlink_sendmsg+0x10/0x10
>   ? __futex_queue+0x10b/0x1f0
>   ____sys_sendmsg+0x7a2/0x950
>   ? copy_msghdr_from_user+0x26b/0x430
>   ? __pfx_____sys_sendmsg+0x10/0x10
>   ? __pfx_copy_msghdr_from_user+0x10/0x10
>   ___sys_sendmsg+0xf8/0x180
>   ? __pfx____sys_sendmsg+0x10/0x10
>   ? __pfx_futex_wait+0x10/0x10
>   ? fdget+0x2e4/0x4a0
>   __sys_sendmsg+0x11f/0x1c0
>   ? __pfx___sys_sendmsg+0x10/0x10
>   do_syscall_64+0xe2/0x570
>   ? exc_page_fault+0x66/0xb0
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
>   </TASK>
> 
> This fix may be combined with another one in the ethtool subsystem:
> https://lore.kernel.org/all/20260322075917.254874-1-alex.popov@linux.com/T/#u
> 
> Fixes: d43c65b05b848e0b ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexander Popov <alex.popov@linux.com>

Reviewed-by: Breno Leitao <leitao@debian.org>

Re: [PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Andrew Lunn]

On Wed, Mar 25, 2026 at 01:46:02AM +0300, Alexander Popov wrote:
> Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
> the virt_wifi net devices. However, unregistering a virt_wifi device in
> netdev_run_todo() can happen together with the device referenced by
> SET_NETDEV_DEV().
> 
> It can result in use-after-free during the ethtool operations performed
> on a virt_wifi device that is currently being unregistered. Such a net
> device can have the `dev.parent` field pointing to the freed memory,
> but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.
> 
> Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:

Did you have a look at all user of SET_NETDEV_DEV() to see if there
are other examples of the same bug?

What i found was:

https://elixir.bootlin.com/linux/v6.19.9/source/drivers/net/ethernet/mellanox/mlx4/en_netdev.c#L3180

Does this have the same problem?

     Andrew

Re: [PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Greg KH]

On Wed, Mar 25, 2026 at 01:34:43PM +0100, Andrew Lunn wrote:
> On Wed, Mar 25, 2026 at 01:46:02AM +0300, Alexander Popov wrote:
> > Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
> > the virt_wifi net devices. However, unregistering a virt_wifi device in
> > netdev_run_todo() can happen together with the device referenced by
> > SET_NETDEV_DEV().
> > 
> > It can result in use-after-free during the ethtool operations performed
> > on a virt_wifi device that is currently being unregistered. Such a net
> > device can have the `dev.parent` field pointing to the freed memory,
> > but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.
> > 
> > Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:
> 
> Did you have a look at all user of SET_NETDEV_DEV() to see if there
> are other examples of the same bug?
> 
> What i found was:
> 
> https://elixir.bootlin.com/linux/v6.19.9/source/drivers/net/ethernet/mellanox/mlx4/en_netdev.c#L3180
> 
> Does this have the same problem?

That's not pointing to the "parent" device, but rather the actual device
under operation from what I can tell.  Or am I mistaking what "pdev"
means here?  Isn't that the pci device the driver is bound to?

thanks,

greg k-h

Re: [PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Alexander Popov]

On 3/25/26 15:34, Andrew Lunn wrote:
> On Wed, Mar 25, 2026 at 01:46:02AM +0300, Alexander Popov wrote:
>> Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
>> the virt_wifi net devices. However, unregistering a virt_wifi device in
>> netdev_run_todo() can happen together with the device referenced by
>> SET_NETDEV_DEV().
>>
>> It can result in use-after-free during the ethtool operations performed
>> on a virt_wifi device that is currently being unregistered. Such a net
>> device can have the `dev.parent` field pointing to the freed memory,
>> but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.
>>
>> Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:
> 
> Did you have a look at all user of SET_NETDEV_DEV() to see if there
> are other examples of the same bug?
> 
> What i found was:
> 
> https://elixir.bootlin.com/linux/v6.19.9/source/drivers/net/ethernet/mellanox/mlx4/en_netdev.c#L3180
> 
> Does this have the same problem?

Andrew, I can't say about this particular net device. Looks like it refers to a 
specific ethernet adapter.

How can we distinguish security-relevant bugs similar to this use-after-free:
an unprivileged user must be able to create a given net device via user namespaces.

As I mentioned, applying this fix in ethtool could help against them:
https://lore.kernel.org/all/20260322075917.254874-1-alex.popov@linux.com/T/#u

Best regards,
Alexander

FAILED: patch "[PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid" failed to apply to 6.19-stable tree

[gregkh]

The patch below does not apply to the 6.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.19.y
git checkout FETCH_HEAD
git cherry-pick -x 789b06f9f39cdc7e895bdab2c034e39c41c8f8d6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026040715-good-overture-8018@gregkh' --subject-prefix 'PATCH 6.19.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 789b06f9f39cdc7e895bdab2c034e39c41c8f8d6 Mon Sep 17 00:00:00 2001
From: Alexander Popov <alex.popov@linux.com>
Date: Wed, 25 Mar 2026 01:46:02 +0300
Subject: [PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid
 use-after-free

Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
the virt_wifi net devices. However, unregistering a virt_wifi device in
netdev_run_todo() can happen together with the device referenced by
SET_NETDEV_DEV().

It can result in use-after-free during the ethtool operations performed
on a virt_wifi device that is currently being unregistered. Such a net
device can have the `dev.parent` field pointing to the freed memory,
but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.

Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:

 ==================================================================
 BUG: KASAN: slab-use-after-free in __pm_runtime_resume+0xe2/0xf0
 Read of size 2 at addr ffff88810cfc46f8 by task pm/606

 Call Trace:
  <TASK>
  dump_stack_lvl+0x4d/0x70
  print_report+0x170/0x4f3
  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
  kasan_report+0xda/0x110
  ? __pm_runtime_resume+0xe2/0xf0
  ? __pm_runtime_resume+0xe2/0xf0
  __pm_runtime_resume+0xe2/0xf0
  ethnl_ops_begin+0x49/0x270
  ethnl_set_features+0x23c/0xab0
  ? __pfx_ethnl_set_features+0x10/0x10
  ? kvm_sched_clock_read+0x11/0x20
  ? local_clock_noinstr+0xf/0xf0
  ? local_clock+0x10/0x30
  ? kasan_save_track+0x25/0x60
  ? __kasan_kmalloc+0x7f/0x90
  ? genl_family_rcv_msg_attrs_parse.isra.0+0x150/0x2c0
  genl_family_rcv_msg_doit+0x1e7/0x2c0
  ? __pfx_genl_family_rcv_msg_doit+0x10/0x10
  ? __pfx_cred_has_capability.isra.0+0x10/0x10
  ? stack_trace_save+0x8e/0xc0
  genl_rcv_msg+0x411/0x660
  ? __pfx_genl_rcv_msg+0x10/0x10
  ? __pfx_ethnl_set_features+0x10/0x10
  netlink_rcv_skb+0x121/0x380
  ? __pfx_genl_rcv_msg+0x10/0x10
  ? __pfx_netlink_rcv_skb+0x10/0x10
  ? __pfx_down_read+0x10/0x10
  genl_rcv+0x23/0x30
  netlink_unicast+0x60f/0x830
  ? __pfx_netlink_unicast+0x10/0x10
  ? __pfx___alloc_skb+0x10/0x10
  netlink_sendmsg+0x6ea/0xbc0
  ? __pfx_netlink_sendmsg+0x10/0x10
  ? __futex_queue+0x10b/0x1f0
  ____sys_sendmsg+0x7a2/0x950
  ? copy_msghdr_from_user+0x26b/0x430
  ? __pfx_____sys_sendmsg+0x10/0x10
  ? __pfx_copy_msghdr_from_user+0x10/0x10
  ___sys_sendmsg+0xf8/0x180
  ? __pfx____sys_sendmsg+0x10/0x10
  ? __pfx_futex_wait+0x10/0x10
  ? fdget+0x2e4/0x4a0
  __sys_sendmsg+0x11f/0x1c0
  ? __pfx___sys_sendmsg+0x10/0x10
  do_syscall_64+0xe2/0x570
  ? exc_page_fault+0x66/0xb0
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  </TASK>

This fix may be combined with another one in the ethtool subsystem:
https://lore.kernel.org/all/20260322075917.254874-1-alex.popov@linux.com/T/#u

Fixes: d43c65b05b848e0b ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Popov <alex.popov@linux.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260324224607.374327-1-alex.popov@linux.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/drivers/net/wireless/virtual/virt_wifi.c b/drivers/net/wireless/virtual/virt_wifi.c
index 885dc7243e8d..97bd39d89e98 100644
--- a/drivers/net/wireless/virtual/virt_wifi.c
+++ b/drivers/net/wireless/virtual/virt_wifi.c
@@ -557,7 +557,6 @@ static int virt_wifi_newlink(struct net_device *dev,
 	eth_hw_addr_inherit(dev, priv->lowerdev);
 	netif_stacked_transfer_operstate(priv->lowerdev, dev);
 
-	SET_NETDEV_DEV(dev, &priv->lowerdev->dev);
 	dev->ieee80211_ptr = kzalloc_obj(*dev->ieee80211_ptr);
 
 	if (!dev->ieee80211_ptr) {

[PATCH] wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free

[Alexander Popov]

Currently we execute `SET_NETDEV_DEV(dev, &priv->lowerdev->dev)` for
the virt_wifi net devices. However, unregistering a virt_wifi device in
netdev_run_todo() can happen together with the device referenced by
SET_NETDEV_DEV().

It can result in use-after-free during the ethtool operations performed
on a virt_wifi device that is currently being unregistered. Such a net
device can have the `dev.parent` field pointing to the freed memory,
but ethnl_ops_begin() calls `pm_runtime_get_sync(dev->dev.parent)`.

Let's remove SET_NETDEV_DEV for virt_wifi to avoid bugs like this:

 ==================================================================
 BUG: KASAN: slab-use-after-free in __pm_runtime_resume+0xe2/0xf0
 Read of size 2 at addr ffff88810cfc46f8 by task pm/606

 Call Trace:
  <TASK>
  dump_stack_lvl+0x4d/0x70
  print_report+0x170/0x4f3
  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
  kasan_report+0xda/0x110
  ? __pm_runtime_resume+0xe2/0xf0
  ? __pm_runtime_resume+0xe2/0xf0
  __pm_runtime_resume+0xe2/0xf0
  ethnl_ops_begin+0x49/0x270
  ethnl_set_features+0x23c/0xab0
  ? __pfx_ethnl_set_features+0x10/0x10
  ? kvm_sched_clock_read+0x11/0x20
  ? local_clock_noinstr+0xf/0xf0
  ? local_clock+0x10/0x30
  ? kasan_save_track+0x25/0x60
  ? __kasan_kmalloc+0x7f/0x90
  ? genl_family_rcv_msg_attrs_parse.isra.0+0x150/0x2c0
  genl_family_rcv_msg_doit+0x1e7/0x2c0
  ? __pfx_genl_family_rcv_msg_doit+0x10/0x10
  ? __pfx_cred_has_capability.isra.0+0x10/0x10
  ? stack_trace_save+0x8e/0xc0
  genl_rcv_msg+0x411/0x660
  ? __pfx_genl_rcv_msg+0x10/0x10
  ? __pfx_ethnl_set_features+0x10/0x10
  netlink_rcv_skb+0x121/0x380
  ? __pfx_genl_rcv_msg+0x10/0x10
  ? __pfx_netlink_rcv_skb+0x10/0x10
  ? __pfx_down_read+0x10/0x10
  genl_rcv+0x23/0x30
  netlink_unicast+0x60f/0x830
  ? __pfx_netlink_unicast+0x10/0x10
  ? __pfx___alloc_skb+0x10/0x10
  netlink_sendmsg+0x6ea/0xbc0
  ? __pfx_netlink_sendmsg+0x10/0x10
  ? __futex_queue+0x10b/0x1f0
  ____sys_sendmsg+0x7a2/0x950
  ? copy_msghdr_from_user+0x26b/0x430
  ? __pfx_____sys_sendmsg+0x10/0x10
  ? __pfx_copy_msghdr_from_user+0x10/0x10
  ___sys_sendmsg+0xf8/0x180
  ? __pfx____sys_sendmsg+0x10/0x10
  ? __pfx_futex_wait+0x10/0x10
  ? fdget+0x2e4/0x4a0
  __sys_sendmsg+0x11f/0x1c0
  ? __pfx___sys_sendmsg+0x10/0x10
  do_syscall_64+0xe2/0x570
  ? exc_page_fault+0x66/0xb0
  entry_SYSCALL_64_after_hwframe+0x77/0x7f
  </TASK>

This fix may be combined with another one in the ethtool subsystem:
https://lore.kernel.org/all/20260322075917.254874-1-alex.popov@linux.com/T/#u

Fixes: d43c65b05b848e0b ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Popov <alex.popov@linux.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://patch.msgid.link/20260324224607.374327-1-alex.popov@linux.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
(cherry picked from commit 789b06f9f39cdc7e895bdab2c034e39c41c8f8d6)
---
 drivers/net/wireless/virtual/virt_wifi.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/wireless/virtual/virt_wifi.c b/drivers/net/wireless/virtual/virt_wifi.c
index 4eae89376feb..cd6b66242bff 100644
--- a/drivers/net/wireless/virtual/virt_wifi.c
+++ b/drivers/net/wireless/virtual/virt_wifi.c
@@ -557,7 +557,6 @@ static int virt_wifi_newlink(struct net_device *dev,
 	eth_hw_addr_inherit(dev, priv->lowerdev);
 	netif_stacked_transfer_operstate(priv->lowerdev, dev);
 
-	SET_NETDEV_DEV(dev, &priv->lowerdev->dev);
 	dev->ieee80211_ptr = kzalloc(sizeof(*dev->ieee80211_ptr), GFP_KERNEL);
 
 	if (!dev->ieee80211_ptr) {
-- 
2.53.0