Subject: Re: [PATCH net v3] net: core: failover: fix NULL pointer dereference in failover_slave_register()

From: Jakub Kicinski <[email-masked]>
Date: Fri, 27 Feb 2026 17:36:49 -0800

On Thu, 26 Feb 2026 13:56:01 +0500 Zeeshan Ahmad wrote:
> Smatch warns that 'fops' is dereferenced without a NULL check.
> While other callbacks in this function properly check 'fops', the
> rx_handler registration does not.
> 
> Consolidate the NULL check for 'fops' at the beginning of the function,
> before it is first used in slave_pre_register(). This ensures 'fops' is
> valid for the entire function scope and allows the removal of redundant
> NULL checks later in the function, as suggested by Dan Carpenter.
> 
> Fixes: 30c8bd5aa8b2 ("net: Introduce generic failover module")

Not really a fix, there's only one user - net_failover and it always
passes the ops and has all callbacks.

> diff --git a/net/core/failover.c b/net/core/failover.c
> index 2a140b3ea669..47e4a91dcaa6 100644
> --- a/net/core/failover.c
> +++ b/net/core/failover.c
> @@ -59,7 +59,10 @@ static int failover_slave_register(struct net_device *slave_dev)
>  	if (!failover_dev)
>  		goto done;
>  
> -	if (fops && fops->slave_pre_register &&
> +	if (WARN_ON_ONCE(!fops))
> +		goto done;

Better still please add this check in failover_register()
so that we don't allow any device to be registered without ops.
Then you can delete all the fops checks throughout this file,
not just in this one function.
-- 
pw-bot: cr