Re: [PATCH v2] nbd: Fix memory leak in nbd_add_socket

["Zhengbin (OSKernel)" <zhengbin13@huawei.com>]

On 2020/6/20 20:05, Markus Elfring wrote:
> > If we add first socket to nbd, config->socks is malloced but
> > num_connections does not update(nsock's allocation fail), the memory
> > is leaked. Cause in later nbd_config_put(), will only free config->socks
> > when num_connections is not 0.
> >
> > Let nsock's allocation first to avoid this.
> I suggest to improve this change description.
> Can an other wording variant be nicer?

em, how about this?


When adding first socket to nbd, if nsock's allocation fails, config->socks

is malloced but num_connections does not update, memory leak will 
occur(Function

nbd_config_put will only free config->socks when num_connections is not 0).

> …
> > +++ b/drivers/block/nbd.c
> > @@ -1037,21 +1037,22 @@  static int nbd_add_socket(struct nbd_device *nbd, unsigned long arg,
> >   		return -EBUSY;
> >   	}
> >
> > +	nsock = kzalloc(sizeof(struct nbd_sock), GFP_KERNEL);
> Please use the following code variant.
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst?id=4333a9b0b67bb4e8bcd91bdd80da80b0ec151162#n854
>
> +	nsock = kzalloc(sizeof(*nsock), GFP_KERNEL);
>
>
> …
> >   	if (!socks) {
> >   		sockfd_put(sock);
> > +		kfree(nsock);
> >   		return -ENOMEM;
> >   	}
> Please take another software design possibility into account.
>
>   	if (!socks) {
> -		sockfd_put(sock);
> -		return -ENOMEM;
> +		kfree(nsock);
> +		goto put_socket;
>   	}
>
>
> Regards,
> Markus
>
> .