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

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Message-ID: <tencent_DE78F66DB82F496F9894B8E826EC8ACE0C0A@qq.com>
Date: Wed, 29 Nov 2023 16:18:19 +0800
From: Edward Adam Davis <eadavis@...com>
To: johannes@...solutions.net
Cc: davem@...emloft.net,
	eadavis@...com,
	edumazet@...gle.com,
	kuba@...nel.org,
	linux-kernel@...r.kernel.org,
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	nathan@...nel.org,
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	netdev@...r.kernel.org,
	pabeni@...hat.com,
	syzbot+62d7eef57b09bfebcd84@...kaller.appspotmail.com,
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	trix@...hat.com
Subject: Re: [PATCH] wifi: mac80211: sband's null check should precede params

On Wed, 29 Nov 2023 07:57:07 +0100, Johannes Berg 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?
No, after applying my patch, it will return due to !sband.

Edward