On October 16, 2018 10:52:58 AM PDT, "Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx> wrote:
>Hi Dmitry,
>
>On 10/16/18 7:21 PM, Dmitry Torokhov wrote:
>> Hi Gustavo,
>>
>> On Tue, Oct 16, 2018 at 01:13:13PM +0200, Gustavo A. R. Silva wrote:
>>> setup.code can be indirectly controlled by user-space, hence leading
>to
>>> a potential exploitation of the Spectre variant 1 vulnerability.
>>>
>>> This issue was detected with the help of Smatch:
>>>
>>> drivers/input/misc/uinput.c:512 uinput_abs_setup() warn: potential
>>> spectre issue 'dev->absinfo' [w] (local cap)
>>>
>>> Fix this by sanitizing setup.code before using it to index
>dev->absinfo.
>>
>> So we are saying that attacker, by repeatedly calling ioctl(...,
>> UI_ABS_SETUP, ...) will be able to poison branch predictor and
>discover
>> another program or kernel secrets? But uinput is a privileged
>interface
>> open to root only, as it allows injecting arbitrary keystrokes into
>the
>> kernel. And since only root can use uinput, meh?
>>
>
>Oh I see... in that case this is a false positive.
>
>Although, I wonder if all these operations are only accessible to root:
>
>static const struct file_operations uinput_fops = {
> .owner = THIS_MODULE,
> .open = uinput_open,
> .release = uinput_release,
> .read = uinput_read,
> .write = uinput_write,
> .poll = uinput_poll,
> .unlocked_ioctl = uinput_ioctl,
>#ifdef CONFIG_COMPAT
> .compat_ioctl = uinput_compat_ioctl,
>#endif
> .llseek = no_llseek,
>};
/dev/uinput must be 0600, or accessible to equally privileged user, or you'll be opening your system to much mischief.
Thanks.
--
Dmitry
