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SubjectRe: [PATCH] Input: uinput - fix Spectre v1 vulnerability
From
Date
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,
};

Thanks for the feedback.
--
Gustavo

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