linux-kernel - Re: [PATCH 02/14] HID: i2c-hid: fix memory corruption due to missing hid declaration

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Date:	Wed, 5 Dec 2012 11:10:54 +0100
From:	Benjamin Tissoires <benjamin.tissoires@...il.com>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	Jiri Kosina <jkosina@...e.cz>, linux-input@...r.kernel.org,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/14] HID: i2c-hid: fix memory corruption due to missing
 hid declaration

On Tue, Dec 4, 2012 at 10:42 PM, Jean Delvare <khali@...ux-fr.org> wrote:
> On Tue,  4 Dec 2012 16:27:43 +0100, Benjamin Tissoires wrote:
>> HID descriptors contains 4 bytes of reserved field.
>> The previous implementation was overriding the next fields in struct i2c_hid.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...il.com>
>> ---
>>  drivers/hid/i2c-hid/i2c-hid.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
>> index 0fbb229..ad771a7 100644
>> --- a/drivers/hid/i2c-hid/i2c-hid.c
>> +++ b/drivers/hid/i2c-hid/i2c-hid.c
>> @@ -68,6 +68,7 @@ struct i2c_hid_desc {
>>       __le16 wVendorID;
>>       __le16 wProductID;
>>       __le16 wVersionID;
>> +     __le32 reserved;
>>  } __packed;
>>
>>  struct i2c_hid_cmd {
>> @@ -778,7 +779,7 @@ static int __devinit i2c_hid_fetch_hid_descriptor(struct i2c_hid *ihid)
>>       }
>>
>>       dsize = le16_to_cpu(hdesc->wHIDDescLength);
>> -     if (!dsize || dsize > HID_MAX_DESCRIPTOR_SIZE) {
>> +     if (!dsize || dsize > sizeof(struct i2c_hid_desc)) {
>
> Shouldn't !dsize rather be dsize < 4? You're reading hdesc->bcdVersion,
> which is only defined if dsize >= 4 if I understand the code correctly.

Yes, you are right. Thanks.

Jiri, this patch is a prerequisite for "[PATCH 10/14] HID: i2c-hid:
reorder allocation/free of buffers".
could you please what for a v2 before applying 10/14?

Cheers,
Benjamin

>
>>               dev_err(&client->dev, "weird size of HID descriptor (%u)\n",
>>                       dsize);
>>               return -ENODEV;
>
>
> --
> Jean Delvare
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