Re: [PATCH] net/dsa: fix oob in dsa_user_prechangeupper

[Vladimir Oltean <olteanv@gmail.com>]

On Tue, Jan 16, 2024 at 10:56:26PM +0800, Edward Adam Davis wrote:
> If the private data is not allocated memory when generating an instance of 
> struct net_device, i.e. priv_size is too small, then its corresponding private
> data should not be accessed.
> 
> Reported-and-tested-by: syzbot+7ec955e36bb239bd720f@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
>  net/dsa/user.h | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/net/dsa/user.h b/net/dsa/user.h
> index 996069130bea..9a40918ee7fc 100644
> --- a/net/dsa/user.h
> +++ b/net/dsa/user.h
> @@ -53,7 +53,11 @@ int dsa_user_manage_vlan_filtering(struct net_device *dev,
>  
>  static inline struct dsa_port *dsa_user_to_port(const struct net_device *dev)
>  {
> -	struct dsa_user_priv *p = netdev_priv(dev);
> +	const struct rtnl_link_ops *ops = dev->rtnl_link_ops;
> +	struct dsa_user_priv *p = ops->priv_size >= sizeof(*p) ? 
> +		netdev_priv(dev) : NULL;
> +	if (!p)
> +		return NULL;
>  
>  	return p->dp;
>  }
> -- 
> 2.43.0
> 

The problem has been fixed by:
https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=844f104790bd

pw-bot: rejected