Re: [PATCH 186/190] Revert "virt: vbox: Only copy_from_user the request-header once"

[Tavis Ormandy]

On 2021-04-21, Greg Kroah-Hartman wrote:
> This reverts commit bd23a7269834dc7c1f93e83535d16ebc44b75eba.
>
> -	*((struct vbg_ioctl_hdr *)buf) = hdr;
> -	if (copy_from_user(buf + sizeof(hdr), (void *)arg + sizeof(hdr),
> -			   hdr.size_in - sizeof(hdr))) {
> +	if (copy_from_user(buf, (void *)arg, hdr.size_in)) {
>  		ret = -EFAULT;
>  		goto out;
>  	}

This one seems like a real bugfix, otherwise there's a double-fetch from
userspace, and a TOCTOU with the hdr fields that could cause a OOB read.

Reviewed-by: Tavis Ormandy <taviso@xxxxxxxxx>

Tavis.


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