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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Denis Efremov' <efremov@linux.com>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Pontus Fuchs <pontus.fuchs@gmail.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        "David S. Miller" <davem@davemloft.net>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [PATCH] ar5523: check NULL before memcpy() in ar5523_cmd()
Thread-Topic: [PATCH] ar5523: check NULL before memcpy() in ar5523_cmd()
Thread-Index: AQHVd5eyJR20opeapUCX0TL00aRlGadEWhCg
Date:   Mon, 30 Sep 2019 15:35:42 +0000
Message-ID: <230cd4f790544b01a26afa26e4186454@AcuMS.aculab.com>
References: <20190930140207.28638-1-efremov@linux.com>
In-Reply-To: <20190930140207.28638-1-efremov@linux.com>
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From: Denis Efremov
> Sent: 30 September 2019 15:02
> 
> memcpy() call with "idata == NULL && ilen == 0" results in undefined
> behavior in ar5523_cmd(). For example, NULL is passed in callchain
> "ar5523_stat_work() -> ar5523_cmd_write() -> ar5523_cmd()". This patch
> adds idata check before memcpy() call in ar5523_cmd() to prevent an
> undefined behavior.
> 
...
> Signed-off-by: Denis Efremov <efremov@linux.com>
> ---
>  drivers/net/wireless/ath/ar5523/ar5523.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ar5523/ar5523.c b/drivers/net/wireless/ath/ar5523/ar5523.c
> index b94759daeacc..f25af5bc5282 100644
> --- a/drivers/net/wireless/ath/ar5523/ar5523.c
> +++ b/drivers/net/wireless/ath/ar5523/ar5523.c
> @@ -255,7 +255,8 @@ static int ar5523_cmd(struct ar5523 *ar, u32 code, const void *idata,
> 
>  	if (flags & AR5523_CMD_FLAG_MAGIC)
>  		hdr->magic = cpu_to_be32(1 << 24);
> -	memcpy(hdr + 1, idata, ilen);
> +	if (idata)
> +		memcpy(hdr + 1, idata, ilen);

That would be better as if (ilen) ...

	David

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