linux-kernel - Re: [v3.11][Regression] HID: hyperv: convert alloc+memcpy to memdup

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Date:	Thu, 19 Dec 2013 12:22:30 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Joseph Salisbury <joseph.salisbury@...onical.com>,
	Dan Carpenter <dan.carpenter@...cle.com>, thomas@...3r.de,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	LKML <linux-kernel@...r.kernel.org>, open@...osl.org,
	HID CORE LAYER <linux-input@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<devel@...uxdriverproject.org>
Subject: Re: [v3.11][Regression] HID: hyperv: convert alloc+memcpy to memdup

Hi

On Thu, Dec 19, 2013 at 11:08 AM, David Herrmann <dh.herrmann@...il.com> wrote:
> Hi
>
> On Thu, Dec 19, 2013 at 10:59 AM, Jiri Kosina <jkosina@...e.cz> wrote:
>> On Thu, 19 Dec 2013, David Herrmann wrote:
>>
>>> > diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
>>> > index 253fe23..81eacd3 100644
>>> > --- a/drivers/hid/hid-core.c
>>> > +++ b/drivers/hid/hid-core.c
>>> > @@ -1334,7 +1334,7 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, int size,
>>> >                 csize--;
>>> >         }
>>> >
>>> > -       rsize = ((report->size - 1) >> 3) + 1;
>>> > +       rsize = ((report->size - 1) >> 3) + 1 + (report->id > 0) + 7;
>>>
>>> Isn't "report->id" already covered by "if (report_enum->numbered)"
>>> above? The test for "id > 0" won't work here as in this case
>>> "report_enum->numbered" must already be set to true by the hid-desc
>>> parser, doesn't it?
>>
>> Right, that one is not correct here, thanks.
>>
>>> Where exactly did you get the +7 from?
>>
>> Please see commit (the one I am not really proud of) 27ce405039bfe6d3.
>
> Eh, I remember.. Ok, but the magic-mouse is BT right? So this commit
> really breaks BT drivers:
>
> commit b1a1442a23776756b254b69786848a94d92445ba
> Author: Jiri Kosina <jkosina@...e.cz>
> Date:   Mon Jun 3 11:27:48 2013 +0200
>
>     HID: core: fix reporting of raw events
>
> Problem is, if the raw_event() callback returned 0 earlier, we just
> skipped raw input reports. However, we now always call the
> hid_report_raw_event() helper. Which is normally fine, but the helper
> expects the input buffer to be of size HID_MAX_REPORT_SIZE, which is
> *not* true for HIDP. So the memset() writes over some random memory.
>
> I don't know exactly how to fix it. HID_MAX_BUFFER_SIZE is too big to
> be allocated on the stack, but we're in atomic-context here so a
> kzalloc(rsize, GFP_ATOMIC) seems overkill. So I guess we'd have to
> look into HIDP to make the skb big enough, but I'm not sure how we can
> achieve that.
>
> So off the top of my head, the best idea is to add "char
> inbuf[HID_MAX_BUFFER_SIZE];" to the hidp_session object in HIDP and
> copy every input-report into the buffer before passing to
> hid_input_report().

As this thread doesn't really contain any oops message nor the exact
driver name (except mentioning hyperv and magicmouse), I fixed a
related bug for HIDP:
  http://thread.gmane.org/gmane.linux.bluez.kernel/41969

A similar patch is *really* required for hid-hyperv.c as it also does
not provide a properly sized buffer to hid_input_report().

David
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