Re: [PATCH net-next v2] netdevsim: reject port addition and clean up ports after a failed reload

[Hangbin Liu]

Hi, 
On Fri, Oct 30, 2026 at 03:13:20AM +0300, Ömer Mete Kaya wrote:
> nsim_drv_port_add() does not check devlink_is_reload_failed(), so ports
> can be added via new_port after a failed reload.  nsim_dev_reload_destroy()
> returns early in that state, leaving them behind.  nsim_drv_remove() then
> hits WARN_ON in bpf_offload_dev_destroy() and a subsequent use-after-free.
> 
> Block port creation with -EIO when reload has failed, and delete any
> leftover ports on the early-return path as a safety net.
> 
> Fixes: 75ba029f3c07 ("netdevsim: implement proper devlink reload")
> Reported-by: syzbot+88435e204734072bf39a@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=88435e204734072bf39a
> Signed-off-by: Ömer Mete Kaya <omermetekaya0@xxxxxxxxx>

Looks Joas has a same issue fix with yours a few hour earlier.

https://lore.kernel.org/netdev/179324296598.34505.11070163314749859668@xxxxxxxxx/

> ---
> Tested with syzbot C reproducer.
> v2: drop Cc:stable and target net-next.
> 
>  drivers/net/netdevsim/dev.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c
> index feb88ccbbced..61f0824ce4d3 100644
> --- a/drivers/net/netdevsim/dev.c
> +++ b/drivers/net/netdevsim/dev.c
> @@ -1697,8 +1697,10 @@ static void nsim_dev_reload_destroy(struct nsim_dev *nsim_dev)
>  {
>  	struct devlink *devlink = priv_to_devlink(nsim_dev);
> 
> -	if (devlink_is_reload_failed(devlink))
> +	if (devlink_is_reload_failed(devlink)) {
> +		nsim_dev_port_del_all(nsim_dev);
>  		return;
> +	}
>  	debugfs_remove(nsim_dev->take_snapshot);
> 
>  	if (nsim_dev_get_vfs(nsim_dev)) {
> @@ -1758,7 +1760,9 @@ int nsim_drv_port_add(struct nsim_bus_dev *nsim_bus_dev, enum nsim_dev_port_type
>  	int err;
> 
>  	devl_lock(priv_to_devlink(nsim_dev));
> -	if (__nsim_dev_port_lookup(nsim_dev, type, port_index))
> +	if (devlink_is_reload_failed(priv_to_devlink(nsim_dev)))
> +		err = -EIO;
> +	else if (__nsim_dev_port_lookup(nsim_dev, type, port_index))
>  		err = -EEXIST;
>  	else
>  		err = __nsim_dev_port_add(nsim_dev, type, port_index, perm_addr);


But yours have an extra guard in nsim_drv_port_add...

Leave this to Jakub decide...

Thanks
Hangbin