linux-kernel - Re: [PATCH net] ice: Add check for kzalloc

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Message-ID: <Y48QhnqUEfNEcC8u@unreal>
Date:   Tue, 6 Dec 2022 11:51:02 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jiasheng Jiang <jiasheng@...as.ac.cn>
Cc:     jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, intel-wired-lan@...ts.osuosl.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] ice: Add check for kzalloc

On Tue, Dec 06, 2022 at 11:08:05AM +0800, Jiasheng Jiang wrote:
> As kzalloc may fail and return NULL pointer,
> it should be better to check the return value
> in order to avoid the NULL pointer dereference.
> 
> Fixes: d6b98c8d242a ("ice: add write functionality for GNSS TTY")
> Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
> ---
>  drivers/net/ethernet/intel/ice/ice_gnss.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

The idea is correct, but please change an implementation to use goto
and proper unwind for whole function. It will remove duplication in the
code which handles tty_port destroys.

Thanks

> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_gnss.c b/drivers/net/ethernet/intel/ice/ice_gnss.c
> index b5a7f246d230..6d3d5e75726b 100644
> --- a/drivers/net/ethernet/intel/ice/ice_gnss.c
> +++ b/drivers/net/ethernet/intel/ice/ice_gnss.c
> @@ -421,7 +421,7 @@ static struct tty_driver *ice_gnss_create_tty_driver(struct ice_pf *pf)
>  	const int ICE_TTYDRV_NAME_MAX = 14;
>  	struct tty_driver *tty_driver;
>  	char *ttydrv_name;
> -	unsigned int i;
> +	unsigned int i, j;
>  	int err;
>  
>  	tty_driver = tty_alloc_driver(ICE_GNSS_TTY_MINOR_DEVICES,
> @@ -462,6 +462,17 @@ static struct tty_driver *ice_gnss_create_tty_driver(struct ice_pf *pf)
>  					       GFP_KERNEL);
>  		pf->gnss_serial[i] = NULL;
>  
> +		if (!pf->gnss_tty_port[i]) {
> +			for (j = 0; j < i; j++) {
> +				tty_port_destroy(pf->gnss_tty_port[j]);
> +				kfree(pf->gnss_tty_port[j]);
> +			}
> +			kfree(ttydrv_name);
> +			tty_driver_kref_put(pf->ice_gnss_tty_driver);
> +
> +			return NULL;
> +		}
> +
>  		tty_port_init(pf->gnss_tty_port[i]);
>  		tty_port_link_device(pf->gnss_tty_port[i], tty_driver, i);
>  	}
> -- 
> 2.25.1
>