Re: [PATCH 1/3] extend get/setrlimit to support setting rlimits external to a process (v3)

[Marcin Slusarz <marcin.slusarz@gmail.com>]

Neil Horman wrote:
> +static ssize_t proc_pid_limit_write(struct file *file, const char __user *buf,
> +		size_t count, loff_t *ppos)
> +{
> +	char *buffer;
> +	char *element, *vmc, *vmm;
> +	struct rlimit new_rlim;
> +	unsigned long flags;
> +	int i;
> +	int index = -1;
> +	size_t wcount = 0;
> +	struct task_struct *task = get_proc_task(file->f_path.dentry->d_inode);
> +
> +
> +	if (*ppos != 0)
> +		goto out;
> +
> +	if (count > 128)
> +		goto out;

Shouldn't proc_pid_limit_write return 0 or some error in this case?
Right now it silently fails...

> +	buffer = kzalloc(128, GFP_KERNEL);
> +
> +	if (!buffer)
> +		goto out;
> +
> +	element = kzalloc(sizeof(buffer), GFP_KERNEL);
> +	vmc = kzalloc(sizeof(buffer), GFP_KERNEL);
> +	vmm = kzalloc(sizeof(buffer), GFP_KERNEL);
> +
> +	if (!element || !vmm || !vmc)
> +		goto out_free;
> +
> +	wcount = count - copy_from_user(buffer, buf, count);
> +	if (wcount < count)
> +		goto out_free;
> +
> +	i = sscanf(buffer, "%s %s %s", element, vmc, vmm);
> +
> +	if (i < 3)
> +		goto out_free;
> +
> +	for (i = 0; i <= strlen(element); i++)
> +		element[i] = tolower(element[i]);
> +
> +	if (!strncmp(vmc, "unlimited", 9))
> +		new_rlim.rlim_cur = RLIM_INFINITY;
> +	else
> +		new_rlim.rlim_cur = simple_strtoull(vmc, NULL, 10);
> +
> +	if (!strncmp(vmm, "unlimited", 9))
> +		new_rlim.rlim_max = RLIM_INFINITY;
> +	else
> +		new_rlim.rlim_max = simple_strtoull(vmm, NULL, 10);
> +
> +	for (i = 0; i < RLIM_NLIMITS; i++) {
> +		if ((lnames[i].match) &&
> +		    !strncmp(element, lnames[i].match,
> +		     strlen(lnames[i].match))) {
> +			index = i;
> +			break;
> +		}
>  	}
>  
> +	if (!lock_task_sighand(task, &flags))
> +		goto out_free;
> +
> +	if ((index >= 0) && (index < RLIM_NLIMITS))
> +		do_setrlimit(index, &new_rlim, task);

Another 2 silent failures:
- when user passed wrong name
- when do_setrlimit failed

> +
> +	unlock_task_sighand(task, &flags);
> +
> +out_free:
> +	kfree(element);
> +	kfree(vmc);
> +	kfree(vmm);
> +	kfree(buffer);
> +out:
> +	*ppos += count;
> +	put_task_struct(task);
>  	return count;
>  }
>