linux-kernel - Re: [PATCH v1] HID: make arrays usage and value to be the same

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Message-ID: <X9e5vl+nw4GQNYEw@google.com>
Date:   Mon, 14 Dec 2020 11:15:10 -0800
From:   Will McVicker <willmcvicker@...gle.com>
To:     Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        security@...nel.org
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, Will Coster <willcoster@...gle.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v1] HID: make arrays usage and value to be the same

On Sat, Dec 05, 2020 at 12:48:48AM +0000, Will McVicker wrote:
> The HID subsystem allows an "HID report field" to have a different
> number of "values" and "usages" when it is allocated. When a field
> struct is created, the size of the usage array is guaranteed to be at
> least as large as the values array, but it may be larger. This leads to
> a potential out-of-bounds write in
> __hidinput_change_resolution_multipliers() and an out-of-bounds read in
> hidinput_count_leds().
> 
> To fix this, let's make sure that both the usage and value arrays are
> the same size.
> 
> Signed-off-by: Will McVicker <willmcvicker@...gle.com>
> ---
>  drivers/hid/hid-core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 56172fe6995c..8a8b2b982f83 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -90,7 +90,7 @@ EXPORT_SYMBOL_GPL(hid_register_report);
>   * Register a new field for this report.
>   */
>  
> -static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages, unsigned values)
> +static struct hid_field *hid_register_field(struct hid_report *report, unsigned usages)
>  {
>  	struct hid_field *field;
>  
> @@ -101,7 +101,7 @@ static struct hid_field *hid_register_field(struct hid_report *report, unsigned
>  
>  	field = kzalloc((sizeof(struct hid_field) +
>  			 usages * sizeof(struct hid_usage) +
> -			 values * sizeof(unsigned)), GFP_KERNEL);
> +			 usages * sizeof(unsigned)), GFP_KERNEL);
>  	if (!field)
>  		return NULL;
>  
> @@ -300,7 +300,7 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
>  	usages = max_t(unsigned, parser->local.usage_index,
>  				 parser->global.report_count);
>  
> -	field = hid_register_field(report, usages, parser->global.report_count);
> +	field = hid_register_field(report, usages);
>  	if (!field)
>  		return 0;
>  
> -- 
> 2.29.2.576.ga3fc446d84-goog
> 

Hi Jiri and Benjamin,

This is a friendly reminder in case this got lost in your inbox.

Thanks,
Will