linux-kernel - Re: [PATCH v3] HID: core: Sanitize event code and type when mapping input

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Date:   Tue, 01 Sep 2020 10:44:28 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v3] HID: core: Sanitize event code and type when mapping
 input

On 2020-08-27 22:05, Marc Zyngier wrote:
> When calling into hid_map_usage(), the passed event code is
> blindly stored as is, even if it doesn't fit in the associated bitmap.
> 
> This event code can come from a variety of sources, including devices
> masquerading as input devices, only a bit more "programmable".
> 
> Instead of taking the event code at face value, check that it actually
> fits the corresponding bitmap, and if it doesn't:
> - spit out a warning so that we know which device is acting up
> - NULLify the bitmap pointer so that we catch unexpected uses
> 
> Code paths that can make use of untrusted inputs can now check
> that the mapping was indeed correct and bail out if not.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
> * From v2:
>   - Don't prematurely narrow the event code so that hid_map_usage()
>     catches illegal values beyond the 16bit limit.
> 
> * From v1:
>   - Dropped the input.c changes, and turned hid_map_usage() into
>     the validation primitive.
>   - Handle mapping failures in hidinput_configure_usage() and
>     mt_touch_input_mapping() (on top of hid_map_usage_clear() which
>     was already handled)
> 
>  drivers/hid/hid-input.c      |  4 ++++
>  drivers/hid/hid-multitouch.c |  2 ++
>  drivers/mfd/syscon.c         |  2 +-
>  include/linux/hid.h          | 42 +++++++++++++++++++++++++-----------
>  4 files changed, 36 insertions(+), 14 deletions(-)
> 

[...]

> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 7a660411c562..75859e492984 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c
> @@ -108,6 +108,7 @@ static struct syscon *of_syscon_register(struct
> device_node *np, bool check_clk)
>  	syscon_config.max_register = resource_size(&res) - reg_io_width;
> 
>  	regmap = regmap_init_mmio(NULL, base, &syscon_config);
> +	kfree(syscon_config.name);
>  	if (IS_ERR(regmap)) {
>  		pr_err("regmap init failed\n");
>  		ret = PTR_ERR(regmap);
> @@ -144,7 +145,6 @@ static struct syscon *of_syscon_register(struct
> device_node *np, bool check_clk)
>  	regmap_exit(regmap);
>  err_regmap:
>  	iounmap(base);
> -	kfree(syscon_config.name);
>  err_map:
>  	kfree(syscon);
>  	return ERR_PTR(ret);


This hunk is totally unrelated, and is from another fix I was working
on at the same time... Sorry for the nois, I'll post v4 (hopefully 
final)
now.

         M.
-- 
Jazz is not dead. It just smells funny...