Re: [PATCH v4 01/11] stm class: Introduce an abstraction for System Trace Module devices

[Sasha Levin <sasha.levin@oracle.com>]

On 09/22/2015 08:47 AM, Alexander Shishkin wrote:
> +static ssize_t stm_char_write(struct file *file, const char __user *buf,
> +			      size_t count, loff_t *ppos)
> +{
> +	struct stm_file *stmf = file->private_data;
> +	struct stm_device *stm = stmf->stm;
> +	char *kbuf;
> +	int err;
> +
> +	/*
> +	 * if no m/c have been assigned to this writer up to this
> +	 * point, use "default" policy entry
> +	 */
> +	if (!stmf->output.nr_chans) {
> +		err = stm_file_assign(stmf, "default", 1);
> +		/*
> +		 * EBUSY means that somebody else just assigned this
> +		 * output, which is just fine for write()
> +		 */
> +		if (err && err != -EBUSY)
> +			return err;
> +	}
> +
> +	kbuf = kmalloc(count + 1, GFP_KERNEL);

This bit allows for user-controllable kmalloc() allocation lengths, including
a possible overflow.


Thanks,
Sasha