Re: [PATCH] ath11k: Fix a NULL pointer dereference in ath11k_mac_op_hw_scan()

From: Jeff Johnson <quic_jjohnson@quicinc.com>
To: Zhou Qingyang <zhou1615@umn.edu>
Cc: <kjlu@umn.edu>, Kalle Valo <kvalo@codeaurora.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Manikanta Pubbisetty <mpubbise@codeaurora.org>,
	Shashidhar Lakkavalli <slakkavalli@datto.com>,
	Govindaraj Saminathan <gsamin@codeaurora.org>,
	Vasanthakumar Thiagarajan <vthiagar@codeaurora.org>,
	Pradeep Kumar Chitrapu <pradeepc@codeaurora.org>,
	<ath11k@lists.infradead.org>, <linux-wireless@vger.kernel.org>,
	<netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ath11k: Fix a NULL pointer dereference in ath11k_mac_op_hw_scan()
Date: Wed, 1 Dec 2021 09:22:36 -0800	[thread overview]
Message-ID: <a29a8153-2a4f-1876-ec48-47e08db00a98@quicinc.com> (raw)
In-Reply-To: <20211130084304.72160-1-zhou1615@umn.edu>

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@umn.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);
>   	}
>   
> 