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Message-ID: <176dd1b5-ee12-fa05-0aa6-e3e031087d6f@broadcom.com>
Date:   Wed, 16 Nov 2022 12:58:28 +0100
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Subject: Re: [PATCH] wifi: brcmfmac: Check the count value of channel spec to
 prevent out-of-bounds reads
To:     Minsuk Kang <linuxlovemin@yonsei.ac.kr>,
        linux-wireless@vger.kernel.org, aspriel@gmail.com
Cc:     dokyungs@yonsei.ac.kr, jisoo.jang@yonsei.ac.kr
References: <20221111075346.136376-1-linuxlovemin@yonsei.ac.kr>
From:   Arend van Spriel <arend.vanspriel@broadcom.com>
In-Reply-To: <20221111075346.136376-1-linuxlovemin@yonsei.ac.kr>
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On 11/11/2022 8:53 AM, Minsuk Kang wrote:
> This patch fixes slab-out-of-bounds reads in brcmfmac that occur in
> brcmf_construct_chaninfo() and brcmf_enable_bw40_2g() when the count
> value of channel specifications provided by the device is greater than
> the length of 'list->element[]', decided by the size of the 'list'
> allocated with kzalloc(). The patch adds checks that make the functions
> free the buffer and return -EINVAL if that is the case. Note that the
> negative return is handled by the caller, brcmf_setup_wiphybands() or
> brcmf_cfg80211_attach().
> 
> Found by a modified version of syzkaller.

[snip]

> Reported-by: Dokyung Song <dokyungs@yonsei.ac.kr>
> Reported-by: Jisoo Jang <jisoo.jang@yonsei.ac.kr>
> Reported-by: Minsuk Kang <linuxlovemin@yonsei.ac.kr>
> Signed-off-by: Minsuk Kang <linuxlovemin@yonsei.ac.kr>
> ---
>   .../broadcom/brcm80211/brcmfmac/cfg80211.c         | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> index ae9507dec74a..3a1c0743e19c 100644
> --- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> +++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cfg80211.c
> @@ -6840,6 +6840,13 @@ static int brcmf_construct_chaninfo(struct brcmf_cfg80211_info *cfg,
>   			band->channels[i].flags = IEEE80211_CHAN_DISABLED;
>   
>   	total = le32_to_cpu(list->count);
> +	if (total > BRCMF_DCMD_MEDLEN / sizeof(__le32) - 1) {

Please add and use macro definition here:

#define BRCMF_MAX_CHANSPEC_LIST		(BRCMF_DCMD_MEDLEN / sizeof(__le32) - 1)

> +		bphy_err(drvr, "Invalid count of channel Spec. (%u)\n",
> +			 total);
> +		err = -EINVAL;
> +		goto fail_pbuf;
> +	}
> +
>   	for (i = 0; i < total; i++) {
>   		ch.chspec = (u16)le32_to_cpu(list->element[i]);
>   		cfg->d11inf.decchspec(&ch);
> @@ -6985,6 +6992,13 @@ static int brcmf_enable_bw40_2g(struct brcmf_cfg80211_info *cfg)
>   		band = cfg_to_wiphy(cfg)->bands[NL80211_BAND_2GHZ];
>   		list = (struct brcmf_chanspec_list *)pbuf;
>   		num_chan = le32_to_cpu(list->count);
> +		if (num_chan > BRCMF_DCMD_MEDLEN / sizeof(__le32) - 1) {

...and here.

> +			bphy_err(drvr, "Invalid count of channel Spec. (%u)\n",
> +				 num_chan);
> +			kfree(pbuf);
> +			return -EINVAL;
> +		}
> +
>   		for (i = 0; i < num_chan; i++) {
>   			ch.chspec = (u16)le32_to_cpu(list->element[i]);
>   			cfg->d11inf.decchspec(&ch);

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