linux-kernel - Re: [PATCH] wifi: brcmfmac: pcie: handle randbuf allocation failure

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Date: Wed, 6 Mar 2024 10:19:58 +0100
From: Arend van Spriel <arend.vanspriel@...adcom.com>
To: Duoming Zhou <duoming@....edu.cn>, linux-kernel@...r.kernel.org
Cc: kvalo@...nel.org, konrad.dybcio@...aro.org, hdegoede@...hat.com,
 minipli@...ecurity.net, linux-wireless@...r.kernel.org,
 brcm80211@...ts.linux.dev, brcm80211-dev-list.pdl@...adcom.com
Subject: Re: [PATCH] wifi: brcmfmac: pcie: handle randbuf allocation failure

On 3/1/2024 2:51 PM, Duoming Zhou wrote:
> The kzalloc() in brcmf_pcie_download_fw_nvram() will return
> null if the physical memory has run out. As a result, if we
> use get_random_bytes() to generate random bytes in the randbuf,
> the null pointer dereference bug will happen.
> 
> Return -ENOMEM from brcmf_pcie_download_fw_nvram() if kzalloc()
> fails for randbuf.
> 
> Fixes: 91918ce88d9f ("wifi: brcmfmac: pcie: Provide a buffer of random bytes to the device")

Looks good to me. Looking for kernel guideline about stack usage to 
determine whether it would be ok to just use buffer on stack. Does 
anyone know. This one is 256 bytes so I guess the allocation is 
warranted here.

Acked-by: Arend van Spriel <arend.vanspriel@...adcom.com>
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> ---
>   drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
> index d7fb88bb6ae..5ab9c902e49 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
> @@ -1730,6 +1730,8 @@ static int brcmf_pcie_download_fw_nvram(struct brcmf_pciedev_info *devinfo,
>   
>   			address -= rand_len;
>   			randbuf = kzalloc(rand_len, GFP_KERNEL);
> +			if (!randbuf)
> +				return -ENOMEM;
>   			get_random_bytes(randbuf, rand_len);
>   			memcpy_toio(devinfo->tcm + address, randbuf, rand_len);
>   			kfree(randbuf);

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