linux-kernel - Re: [PATCH 1/2] HID: core: i2c-hid: fix size check and type usage

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Date:   Sat, 3 Feb 2018 09:36:51 +0100
From:   Marcus Folkesson <marcus.folkesson@...il.com>
To:     Aaron Ma <aaron.ma@...onical.com>
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        jikos@...nel.org, benjamin.tissoires@...hat.com
Subject: Re: [PATCH 1/2] HID: core: i2c-hid: fix size check and type usage

Hi Aaron,

On Wed, Jan 03, 2018 at 01:30:05AM +0800, Aaron Ma wrote:
> When convert char array with signed int, if the inbuf[x] is negative then
> upper bits will be set to 1. Fix this by using u8 instead of char.
> 
> ret_size has to be at least 3, hid_input_report use it after minus 2 bytes.

At least 2?
hid_input_report() checks (!size)

> 
> size should be more than 0 to keep memset safe.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Aaron Ma <aaron.ma@...onical.com>
> ---
>  drivers/hid/hid-core.c        |  4 ++--
>  drivers/hid/i2c-hid/i2c-hid.c | 10 +++++-----
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
> index 0c3f608131cf..992547771d96 100644
> --- a/drivers/hid/hid-core.c
> +++ b/drivers/hid/hid-core.c
> @@ -1506,7 +1506,7 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, int size,
>  	if (rsize > HID_MAX_BUFFER_SIZE)
>  		rsize = HID_MAX_BUFFER_SIZE;
>  
> -	if (csize < rsize) {
> +	if ((csize < rsize) && (csize > 0)) {
>  		dbg_hid("report %d is too short, (%d < %d)\n", report->id,
>  				csize, rsize);
>  		memset(cdata + csize, 0, rsize - csize);
> @@ -1566,7 +1566,7 @@ int hid_input_report(struct hid_device *hid, int type, u8 *data, int size, int i
>  	report_enum = hid->report_enum + type;
>  	hdrv = hid->driver;
>  
> -	if (!size) {
> +	if (size <= 0) {

All code that is using hid_input_report() seems to check that no
negative size is provided.

If we want this check, maybe we should consider making size unsigned
instead?

>  		dbg_hid("empty report\n");
>  		ret = -1;
>  		goto unlock;
> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> index e054ee43c1e2..09404ffdb08b 100644
> --- a/drivers/hid/i2c-hid/i2c-hid.c
> +++ b/drivers/hid/i2c-hid/i2c-hid.c
> @@ -144,10 +144,10 @@ struct i2c_hid {
>  						   * register of the HID
>  						   * descriptor. */
>  	unsigned int		bufsize;	/* i2c buffer size */
> -	char			*inbuf;		/* Input buffer */
> -	char			*rawbuf;	/* Raw Input buffer */
> -	char			*cmdbuf;	/* Command buffer */
> -	char			*argsbuf;	/* Command arguments buffer */
> +	u8			*inbuf;		/* Input buffer */
> +	u8			*rawbuf;	/* Raw Input buffer */
> +	u8			*cmdbuf;	/* Command buffer */
> +	u8			*argsbuf;	/* Command arguments buffer */

Looks good

>  
>  	unsigned long		flags;		/* device flags */
>  	unsigned long		quirks;		/* Various quirks */
> @@ -473,7 +473,7 @@ static void i2c_hid_get_input(struct i2c_hid *ihid)
>  
>  	ret_size = ihid->inbuf[0] | ihid->inbuf[1] << 8;
>  
> -	if (!ret_size) {
> +	if (ret_size <= 2) {

if (ret_size < 2) ?


>  		/* host or device initiated RESET completed */
>  		if (test_and_clear_bit(I2C_HID_RESET_PENDING, &ihid->flags))
>  			wake_up(&ihid->wait);
> -- 
> 2.14.3


Best regards
Marcus Folkesson

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