Re: [RFC v3 2/2] HID: core: Check to ensure report responses match the request

[Benjamin Tissoires <bentiss@kernel.org>]

On Mar 17 2026, Lee Jones wrote:
> On Mon, 16 Mar 2026, Benjamin Tissoires wrote:
> 
> > On Mar 09 2026, Lee Jones wrote:
> > > It is possible for a malicious (or clumsy) device to respond to a
> > > specific report's feature request using a completely different report
> > > ID.  This can cause confusion in the HID core resulting in nasty
> > > side-effects such as OOB writes.
> > > 
> > > Add a check to ensure that the report ID in the response, matches the
> > > one that was requested.
> > > 
> > > Signed-off-by: Lee Jones <lee@kernel.org>
> > > ---
> > > v2 -> v3: Cover more bases by moving the check up a layer from MT to HID Core
> > > 
> > > RFC query: Is this always okay?
> > >            Should the report number always match the request?
> > > 	   Are there legitimate times where the two would differ?
> > 
> > Technically, there is no reasons for a HID_SET_REPORT request to change
> > the incoming buffer. So that test might break it.
> > 
> > I prefered fixing the calling sites (hid-multitouch and others), because
> > here we are making decisions on the device behaviour which is not ours
> > to make. More specifically, such a test will prevent us to fix a bogus
> > device by plainly rejecting the call after the facts.
> 
> Okay, so this one is a NACK?  No changes, do not resend?
> 

Yes, NACK on this one. I've merged the hid-multitouch one which wasn't
using the API correctly, please send a followup for the other similar
cases.

Cheers,
Benjamin