linux-kernel - Re: [PATCH v2] s390/raw3270: Handle memory allocation failures in raw3270_setup

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Date: Tue, 25 Jun 2024 08:31:39 +0200
From: Heiko Carstens <hca@...ux.ibm.com>
To: yskelg@...il.com
Cc: Harald Freudenberger <freude@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Markus Elfring <Markus.Elfring@....de>,
        MichelleJin <shjy180909@...il.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] s390/raw3270: Handle memory allocation failures in
 raw3270_setup_console()

On Tue, Jun 25, 2024 at 10:32:26AM +0900, yskelg@...il.com wrote:
> From: Yunseong Kim <yskelg@...il.com>
> 
> A null pointer is stored in a local variable after a call of the function
> "kzalloc" failed. This pointer was passed to a subsequent call of the
> function "raw3270_setup_device" where an undesirable dereference will be
> performed then. Thus add corresponding return value checks.
> The allocated each memory areas are immediately overwritten by the called
> function zero-initialisation be omitted by calling the "kmalloc" instead.
> After "ccw_device_enable_console" succeeds, set the bit raw3270 flag to
> RAW3270_FLAGS_CONSOLE.
> 
> Fixes: 33403dcfcdfd ("[S390] 3270 console: convert from bootmem to slab")
> Cc: linux-s390@...r.kernel.org
> Signed-off-by: Yunseong Kim <yskelg@...il.com>
> ---
>  drivers/s390/char/raw3270.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
...
>  	rc = raw3270_setup_device(cdev, rp, ascebc);
> -	if (rc)
> +	if (rc) {
> +		kfree(ascebc);
> +		kfree(rp);
>  		return ERR_PTR(rc);
> -	set_bit(RAW3270_FLAGS_CONSOLE, &rp->flags);
> -
> +	}
>  	rc = ccw_device_enable_console(cdev);
>  	if (rc) {
>  		ccw_device_destroy_console(cdev);
> +		kfree(ascebc);
> +		kfree(rp);
>  		return ERR_PTR(rc);
>  	}
> +	set_bit(RAW3270_FLAGS_CONSOLE, &rp->flags);

Why did you move the set_bit() call?