linux-kernel - Re: [PATCH v3 2/3] staging: rtl8712: fix uninit-value in r871xu_drv

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Date:   Fri, 6 May 2022 15:27:56 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Wang Cheng <wanngchenng@...il.com>, dan.carpenter@...cle.com
Cc:     linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] staging: rtl8712: fix uninit-value in
 r871xu_drv_init()

Hi Wang,

On 5/6/22 14:59, Wang Cheng wrote:
> Reported-and-tested-by: syzbot+6f5ecd144854c0d8580b@...kaller.appspotmail.com
> Signed-off-by: Wang Cheng <wanngchenng@...il.com>
> ---
>   drivers/staging/rtl8712/usb_intf.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/rtl8712/usb_intf.c b/drivers/staging/rtl8712/usb_intf.c
> index ee4c61f85a07..50dcd3ecb685 100644
> --- a/drivers/staging/rtl8712/usb_intf.c
> +++ b/drivers/staging/rtl8712/usb_intf.c
> @@ -538,13 +538,13 @@ static int r871xu_drv_init(struct usb_interface *pusb_intf,
>   		} else {
>   			AutoloadFail = false;
>   		}
> -		if (((mac[0] == 0xff) && (mac[1] == 0xff) &&
> +		if ((!AutoloadFail) ||
> +		    ((mac[0] == 0xff) && (mac[1] == 0xff) &&
>   		     (mac[2] == 0xff) && (mac[3] == 0xff) &&
>   		     (mac[4] == 0xff) && (mac[5] == 0xff)) ||
>   		    ((mac[0] == 0x00) && (mac[1] == 0x00) &&
>   		     (mac[2] == 0x00) && (mac[3] == 0x00) &&
> -		     (mac[4] == 0x00) && (mac[5] == 0x00)) ||
> -		     (!AutoloadFail)) {
> +		     (mac[4] == 0x00) && (mac[5] == 0x00))) {
>   			mac[0] = 0x00;
>   			mac[1] = 0xe0;
>   			mac[2] = 0x4c;

Hmm,

the whole r871xu_drv_init() looks odd, but it's unrelated.

I see that this patch does not help with below kernel path

r871xu_drv_init()
   if (tmpU1b & _EEPROM_EN) <- true [1]
	if (!r8712_initmac || !mac_pton(r8712_initmac, mac)) <- (*)
		if ((!AutoloadFail) ||	<- false, since [1] branch taken
			[code touches stack data]

(*) false because of r8712_initmac is equal to NULL


I saw, that syzbot said OK on your patch, but it's because you have just 
hided an error inside read API



With regards,
Pavel Skripkin

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