linux-kernel - Re: [PATCH] ath11k: Fix a NULL pointer dereference in ath11k_mac_op_hw

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Date:   Wed, 1 Dec 2021 09:22:36 -0800
From:   Jeff Johnson <quic_jjohnson@...cinc.com>
To:     Zhou Qingyang <zhou1615@....edu>
CC:     <kjlu@....edu>, Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Manikanta Pubbisetty <mpubbise@...eaurora.org>,
        Shashidhar Lakkavalli <slakkavalli@...to.com>,
        Govindaraj Saminathan <gsamin@...eaurora.org>,
        Vasanthakumar Thiagarajan <vthiagar@...eaurora.org>,
        Pradeep Kumar Chitrapu <pradeepc@...eaurora.org>,
        <ath11k@...ts.infradead.org>, <linux-wireless@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ath11k: Fix a NULL pointer dereference in
 ath11k_mac_op_hw_scan()

On 11/30/2021 12:43 AM, Zhou Qingyang wrote:
> In ath11k_mac_op_hw_scan(), the return value of kzalloc() is directly
> used in memcpy(), which may lead to a NULL pointer dereference on
> failure of kzalloc().
> 
> Fix this bug by adding a check of arg.extraie.ptr.
> 
> This bug was found by a static analyzer. The analysis employs
> differential checking to identify inconsistent security operations
> (e.g., checks or kfrees) between two code paths and confirms that the
> inconsistent operations are not recovered in the current function or
> the callers, so they constitute bugs.
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
> Builds with CONFIG_ATH11K=m show no new warnings, and our static
> analyzer no longer warns about this code.
> 
> Fixes: d5c65159f289 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
> Signed-off-by: Zhou Qingyang <zhou1615@....edu>
> ---
>   drivers/net/wireless/ath/ath11k/mac.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath11k/mac.c b/drivers/net/wireless/ath/ath11k/mac.c
> index 1cc55602787b..095f1f9b7611 100644
> --- a/drivers/net/wireless/ath/ath11k/mac.c
> +++ b/drivers/net/wireless/ath/ath11k/mac.c
> @@ -3237,8 +3237,13 @@ static int ath11k_mac_op_hw_scan(struct ieee80211_hw *hw,
>   	arg.scan_id = ATH11K_SCAN_ID;
>   
>   	if (req->ie_len) {
> -		arg.extraie.len = req->ie_len;
>   		arg.extraie.ptr = kzalloc(req->ie_len, GFP_KERNEL);

Your patch looks good, but since you are touching this code IMO this 
should be changed to kmemdup() and we should remove the memcpy() below.

> +		if (!arg.extraie.ptr) {
> +			ret = -ENOMEM;
> +			goto exit;
> +		}
> +
> +		arg.extraie.len = req->ie_len;
>   		memcpy(arg.extraie.ptr, req->ie, req->ie_len);
>   	}
>   
>