linux-kernel - Re: [PATCH] Input: uinput - fix crash when mixing old and new init style

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Message-ID: <20170201084925.GD31658@mail.corp.redhat.com>
Date:   Wed, 1 Feb 2017 09:49:25 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-input@...r.kernel.org,
        David Herrmann <dh.herrmann@...il.com>,
        Rodrigo Rivas Costa <rodrigorivascosta@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Input: uinput - fix crash when mixing old and new init
 style

On Jan 31 2017 or thereabouts, Dmitry Torokhov wrote:
> If user tries to initialize uinput device mixing old and new style
> initialization (i.e. using old UI_SET_ABSBIT instead of UI_ABS_SETUP,
> we forget to allocate input->absinfo and will crash when trying to send
> absolute events:
> 
>         ioctl(ui, UI_DEV_SETUP, &us);
>         ioctl(ui, UI_SET_EVBIT, EV_ABS);
>         ioctl(ui, UI_SET_ABSBIT, ABS_X);
>         ioctl(ui, UI_SET_ABSBIT, ABS_Y);
>         ioctl(ui, UI_DEV_CREATE, 0);

Shouldn't we prevent completely the mix of the 2 versions? If the user
used UI_DEV_SETUP, we should probably prevent the use of UI_SET_ABSBIT
afterwards, or at least warn it somehow.

But the patch in itself doesn't hurt, so:
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

Cheers,
Benjamin

> 
> Reported-by: Rodrigo Rivas Costa <rodrigorivascosta@...il.com>
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=191811
> Fixes: fbae10db0940 ("Input: uinput - rework ABS validation")
> Cc: stable@...r.kernel.org
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> ---
>  drivers/input/misc/uinput.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
> index 92595b98e7ed..022be0e22eba 100644
> --- a/drivers/input/misc/uinput.c
> +++ b/drivers/input/misc/uinput.c
> @@ -263,13 +263,21 @@ static int uinput_create_device(struct uinput_device *udev)
>  		return -EINVAL;
>  	}
>  
> -	if (test_bit(ABS_MT_SLOT, dev->absbit)) {
> -		nslot = input_abs_get_max(dev, ABS_MT_SLOT) + 1;
> -		error = input_mt_init_slots(dev, nslot, 0);
> -		if (error)
> +	if (test_bit(EV_ABS, dev->evbit)) {
> +		input_alloc_absinfo(dev);
> +		if (!dev->absinfo) {
> +			error = -EINVAL;
>  			goto fail1;
> -	} else if (test_bit(ABS_MT_POSITION_X, dev->absbit)) {
> -		input_set_events_per_packet(dev, 60);
> +		}
> +
> +		if (test_bit(ABS_MT_SLOT, dev->absbit)) {
> +			nslot = input_abs_get_max(dev, ABS_MT_SLOT) + 1;
> +			error = input_mt_init_slots(dev, nslot, 0);
> +			if (error)
> +				goto fail1;
> +		} else if (test_bit(ABS_MT_POSITION_X, dev->absbit)) {
> +			input_set_events_per_packet(dev, 60);
> +		}
>  	}
>  
>  	if (test_bit(EV_FF, dev->evbit) && !udev->ff_effects_max) {
> -- 
> 2.11.0.483.g087da7b7c-goog
> 
> -- 
> Dmitry