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

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Date: Tue, 27 Feb 2024 20:40:40 +0100
From: Arend van Spriel <arend.vanspriel@...adcom.com>
To: Joe Perches <joe@...ches.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 2/27/2024 12:42 PM, Joe Perches wrote:
> 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.

Right. That is what I did after which I replied on Feb 18 to your email.

https://lore.kernel.org/all/3e1f11b3-a689-4c8e-bfda-b43649db7106@broadcom.com/

Regards,
Arend

>>
>>> 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;
>>>    }
> 

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