Re: [PATCH RFC v2] tpm: tpm_vtpm_proxy: do not reference kernel memory as user memory

[Stefan Berger]

On 5/29/23 22:01, Jarkko Sakkinen wrote:
> From: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxx>

> -	rc = copy_to_user(buf, proxy_dev->buffer, len);
> +	if (buf)
> +		rc = copy_to_user(buf, proxy_dev->buffer, len);
> +

Looking through other drivers it seems buf is always expected to be a valid non-NULL pointer on file_operations.read().


https://elixir.bootlin.com/linux/latest/source/arch/x86/mm/tlb.c#L1279   simple_read_from_buffer will pass the pointer to the user buffer along and it ('to') ends up in copy_to_user(to, ...);


Same here: https://elixir.bootlin.com/linux/latest/source/security/integrity/ima/ima_fs.c#L41