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

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Date: Tue, 27 Feb 2024 21:44:43 +0800 (GMT+08:00)
From: duoming@....edu.cn
To: "Joe Perches" <joe@...ches.com>
Cc: "Arend van Spriel" <arend.vanspriel@...adcom.com>,
	linux-kernel@...r.kernel.org, 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, 27 Feb 2024 03:42:13 -0800 Joe Perches 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.

There are three functions that call the brcmf_pmksa_v3_op(),
including brcmf_cfg80211_set_pmksa(), brcmf_cfg80211_del_pmksa()
and brcmf_cfg80211_flush_pmksa(). The return type of the above
three functions is s32. If brcmf_pmksa_v3_op() returns -ENOMEM,
the above three functions will also return -ENOMEM. It could be
handled appropriately by the callers of the function. So I think
the simple return of -ENOMEM is appropriate.

> > > 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;
> > >   }

Best regards,
Duoming Zhou