linux-kernel - Re: [PATCH] media: isl6421: fix possible uninitialized-variable access in isl6421_set

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Message-ID: <20211119162831.7f3b39a0@sal.lan>
Date:   Fri, 19 Nov 2021 16:28:31 +0000
From:   Mauro Carvalho Chehab <mchehab@...nel.org>
To:     Tuo Li <islituo@...il.com>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        baijiaju1990@...il.com, TOTE Robot <oslab@...nghua.edu.cn>
Subject: Re: [PATCH] media: isl6421: fix possible uninitialized-variable
 access in isl6421_set_voltage()

Em Sat, 31 Jul 2021 00:38:06 -0700
Tuo Li <islituo@...il.com> escreveu:

> A memory block is allocated through kmalloc(), and its return value is
> assigned to the pointer isl6421. Then isl6421 is assigned to the
> varialbe fe->sec_priv. The function isl6421_set_voltage() is called with
> the argument fe. In this function, fe->sec_priv is assigned to isl6421.
> Thus the pointer isl6421 in the function isl6421_attach() and the function
> isl6421_set_voltage() point to the same memory. However, isl6421->is_off
> is not initialized but it is accessed at line 75:
>   if (isl6421->is_off && !is_off)
> 
> To fix this possible uninitialized-variable access, isl6421->is_off is
> initialized to false in the function isl6421_attach().
> 
> Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
> Signed-off-by: Tuo Li <islituo@...il.com>
> ---
>  drivers/media/dvb-frontends/isl6421.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/dvb-frontends/isl6421.c b/drivers/media/dvb-frontends/isl6421.c
> index 43b0dfc6f453..ea101f66ea88 100644
> --- a/drivers/media/dvb-frontends/isl6421.c
> +++ b/drivers/media/dvb-frontends/isl6421.c
> @@ -185,6 +185,7 @@ struct dvb_frontend *isl6421_attach(struct dvb_frontend *fe, struct i2c_adapter
>  	isl6421->config = ISL6421_ISEL1;
>  	isl6421->i2c = i2c;
>  	isl6421->i2c_addr = i2c_addr;
> +	isl6421->is_off = false;
>  	fe->sec_priv = isl6421;

No need. The driver always initialize it:

        /* default configuration */
        isl6421->config = ISL6421_ISEL1;
        isl6421->i2c = i2c;
        isl6421->i2c_addr = i2c_addr;
        fe->sec_priv = isl6421;
 
        /* bits which should be forced to '1' */
        isl6421->override_or = override_set;
 
        /* bits which should be forced to '0' */
        isl6421->override_and = ~override_clear;
 
        /* detect if it is present or not */
        if (isl6421_set_voltage(fe, SEC_VOLTAGE_OFF)) {
                kfree(isl6421);
                fe->sec_priv = NULL;
                return NULL;
        }
 
        isl6421->is_off = true;
	^^^^^^^^^^^^^^^^^^^^^^^

(except if errors, in which case the struct is freed)

It sounds that your bot is misleading you to write an useless patch

;-)

Regards,
Mauro