linux-kernel - Re: [PATCH] um: NULL check before kfree is not needed

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Message-ID: <3b72e9da-c4ac-cee0-1833-7c2b346fcc28@cambridgegreys.com>
Date:   Sat, 4 Aug 2018 17:05:28 +0100
From:   Anton Ivanov <anton.ivanov@...bridgegreys.com>
To:     YueHaibing <yuehaibing@...wei.com>, jdike@...toit.com,
        richard@....at, christophe.jaillet@...adoo.fr,
        keescook@...omium.org
Cc:     linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: NULL check before kfree is not needed

On 03/08/18 07:39, YueHaibing wrote:

> kfree(NULL) is safe,so this removes NULL check before freeing the mem
>
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>   arch/um/drivers/vector_kern.c | 15 +++++----------
>   arch/um/drivers/vector_user.c |  6 ++----
>   arch/um/kernel/irq.c          |  3 +--
>   3 files changed, 8 insertions(+), 16 deletions(-)
>
> diff --git a/arch/um/drivers/vector_kern.c b/arch/um/drivers/vector_kern.c
> index 50ee3bb..c84133c 100644
> --- a/arch/um/drivers/vector_kern.c
> +++ b/arch/um/drivers/vector_kern.c
> @@ -1118,16 +1118,11 @@ static int vector_net_close(struct net_device *dev)
>   		os_close_file(vp->fds->tx_fd);
>   		vp->fds->tx_fd = -1;
>   	}
> -	if (vp->bpf != NULL)
> -		kfree(vp->bpf);
> -	if (vp->fds->remote_addr != NULL)
> -		kfree(vp->fds->remote_addr);
> -	if (vp->transport_data != NULL)
> -		kfree(vp->transport_data);
> -	if (vp->header_rxbuffer != NULL)
> -		kfree(vp->header_rxbuffer);
> -	if (vp->header_txbuffer != NULL)
> -		kfree(vp->header_txbuffer);
> +	kfree(vp->bpf);
> +	kfree(vp->fds->remote_addr);
> +	kfree(vp->transport_data);
> +	kfree(vp->header_rxbuffer);
> +	kfree(vp->header_txbuffer);
>   	if (vp->rx_queue != NULL)
>   		destroy_queue(vp->rx_queue);
>   	if (vp->tx_queue != NULL)
> diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
> index 4d6a78e..3d8cdbd 100644
> --- a/arch/um/drivers/vector_user.c
> +++ b/arch/um/drivers/vector_user.c
> @@ -267,8 +267,7 @@ static struct vector_fds *user_init_raw_fds(struct arglist *ifspec)
>   		os_close_file(rxfd);
>   	if (txfd >= 0)
>   		os_close_file(txfd);
> -	if (result != NULL)
> -		kfree(result);
> +	kfree(result);
>   	return NULL;
>   }
>   
> @@ -434,8 +433,7 @@ static struct vector_fds *user_init_socket_fds(struct arglist *ifspec, int id)
>   	if (fd >= 0)
>   		os_close_file(fd);
>   	if (result != NULL) {
> -		if (result->remote_addr != NULL)
> -			kfree(result->remote_addr);
> +		kfree(result->remote_addr);
>   		kfree(result);
>   	}
>   	return NULL;
> diff --git a/arch/um/kernel/irq.c b/arch/um/kernel/irq.c
> index 6b7f382..8360fa3 100644
> --- a/arch/um/kernel/irq.c
> +++ b/arch/um/kernel/irq.c
> @@ -244,8 +244,7 @@ static void garbage_collect_irq_entries(void)
>   			to_free = NULL;
>   		}
>   		walk = walk->next;
> -		if (to_free != NULL)
> -			kfree(to_free);
> +		kfree(to_free);
>   	}
>   }
>   
kfree in both slab and slob check for NULLs before freeing so this is 
correct. Thanks for noticing.

Richard, please apply,

A.