linux-kernel - Re: [PATCH] wifi: mac80211: sband's null check should precede params

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Date:   Wed, 29 Nov 2023 07:57:07 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     Edward Adam Davis <eadavis@...com>,
        syzbot+62d7eef57b09bfebcd84@...kaller.appspotmail.com
Cc:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        llvm@...ts.linux.dev, nathan@...nel.org, ndesaulniers@...gle.com,
        netdev@...r.kernel.org, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com, trix@...hat.com
Subject: Re: [PATCH] wifi: mac80211: sband's null check should precede params

On Wed, 2023-11-29 at 13:48 +0800, Edward Adam Davis wrote:
> 
> [Analysis]
> When ieee80211_get_link_sband() fails to find a valid sband and first checks 
> for params in sta_link_apply_parameters(), it will return 0 due to new_link 
> being 0, which will lead to an incorrect process after sta_apply_parameters().
> 
> [Fix]
> First obtain sband and perform a non null check before checking the params.

Not sure I can even disagree with that analysis, it seems right, but ...

> +	if (!link || !link_sta)
> +		return -EINVAL;
> +
> +	sband = ieee80211_get_link_sband(link);
> +	if (!sband)
> +		return -EINVAL;
> +
>  	/*
>  	 * If there are no changes, then accept a link that doesn't exist,
>  	 * unless it's a new link.

There's a comment here which is clearly not true after this change,
since you've already returned for !link_sta?

johannes