linux-kernel - Re: [PATCH] wifi: brcm80211: handle pmk

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Date: Tue, 27 Feb 2024 03:42:13 -0800
From: Joe Perches <joe@...ches.com>
To: Arend van Spriel <arend.vanspriel@...adcom.com>, Duoming Zhou
	 <duoming@....edu.cn>, linux-kernel@...r.kernel.org
Cc: brcm80211-dev-list.pdl@...adcom.com, brcm80211@...ts.linux.dev, 
 linux-wireless@...r.kernel.org, justinstitt@...gle.com, john@...ping.me.uk,
  quic_alokad@...cinc.com, marcan@...can.st, johannes.berg@...el.com, 
 linus.walleij@...aro.org, kvalo@...nel.org
Subject: Re: [PATCH] wifi: brcm80211: handle pmk_op allocation failure

On Tue, 2024-02-27 at 12:21 +0100, Arend van Spriel wrote:
> On 2/27/2024 9:06 AM, Duoming Zhou wrote:
> > The kzalloc() in brcmf_pmksa_v3_op() will return null if the
> > physical memory has run out. As a result, if we dereference
> > the null value, the null pointer dereference bug will happen.
> > 
> > Return -ENOMEM from brcmf_pmksa_v3_op() if kzalloc() fails
> > for pmk_op.
> 
> NAK (see below)
> 
> Also this issue was reported earlier by Joe Perches. Not sure if he 
> wants to be mentioned as such.

I think it's unimportant to be mentioned.

I think it's more important that the code be researched
that the simple return of -ENOMEM the appropriate fix
and is handled by all possible callers of the function.

> 
> > Fixes: a96202acaea4 ("wifi: brcmfmac: cfg80211: Add support for PMKID_V3 operations")
> > Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> > ---
> >   drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.cq b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> > index 28d6a30cc01..3b420b33188 100644
> > --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> > +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> > @@ -4322,6 +4322,10 @@ brcmf_pmksa_v3_op(struct brcmf_if *ifp, struct cfg80211_pmksa *pmksa,
> >   	int ret;
> >   
> >   	pmk_op = kzalloc(sizeof(*pmk_op), GFP_KERNEL);
> > +	if (!pmk_op) {
> > +		ret = -ENOMEM;
> > +		goto out;
> > +	}
> 
> There is really no need to introduce a new label for this. Although you 
> can kfree() a NULL pointer there is no need to do so when you know 
> already it is NULL. Just return -ENOMEM and be done with it.
> 
> Regards,
> Arend
> 
> >   	pmk_op->version = cpu_to_le16(BRCMF_PMKSA_VER_3);
> >   
> >   	if (!pmksa) {
> > @@ -4340,6 +4344,7 @@ brcmf_pmksa_v3_op(struct brcmf_if *ifp, struct cfg80211_pmksa *pmksa,
> >   	pmk_op->length = cpu_to_le16(length);
> >   
> >   	ret = brcmf_fil_iovar_data_set(ifp, "pmkid_info", pmk_op, sizeof(*pmk_op));
> > +out:
> >   	kfree(pmk_op);
> >   	return ret;
> >   }