Re: [PATCH 1/1] HID: uhid: Fix out-of-bounds write caused by raw events mismanagement

[Lee Jones]

On Thu, 26 Feb 2026, Benjamin Tissoires wrote:

> On Feb 26 2026, Lee Jones wrote:
> > On Thu, 26 Feb 2026, Benjamin Tissoires wrote:
> > 
> > > On Feb 26 2026, Lee Jones wrote:
> > > > On Tue, 24 Feb 2026, Jiri Kosina wrote:
> > > > 
> > > > > On Tue, 24 Feb 2026, Benjamin Tissoires wrote:
> > > > > 
> > > > > > Long story short: that patch is too intrusive as it makes assumption on
> > > > > > the behavior of the device. We need to understand where/if the bug was
> > > > > > spotted and fix the caller of hid_hw_raw_request, not the uhid
> > > > > > implementation.
> > > > > 
> > > > > Thanks a lot for the analysis, Benjamin!
> > > > > 
> > > > > I asked about that here:
> > > > > 
> > > > > 	https://lore.kernel.org/all/172q4775-616s-p7s4-7n80-p8579n0r3516@xxxxxxxxxx/
> > > > > 
> > > > > So let's wait for Lee to clarify. Until that, the patch stays out of the 
> > > > > branch.
> > > > 
> > > > Thanks to both of you for looking into this.  I appreciate your efforts.
> > > > 
> > > > This is very much real world.
> > > > 
> > > > Is there a way to add an errata for the PS3 controller?
> > > > 
> > > 
> > > Unfortunatelly no. uhid merely emulates what a device can do, and HID is
> > > a convention. So if we were to have a special case to PS3 controllers,
> > > we would then start having to maintain an endless list of quirks when
> > > the issue is *not* in uhid, but in the processing of the device after
> > > (maybe in hid-core?).
> > 
> > Actually I think the issue is in UHID.  At least the way I read it.
> 
> And I disagree :)
> 
> > 
> > Are there legitimate use-cases for devices overwriting the Report ID
> > contained in the first index of the data buffer?  From my very limited
> > knowledge of the subsystem, this sounds like an oversight.
> > 
> 
> Legitimate, probably no, but we are talking about physical devices
> here. uhid is a mere replacement of a transport layer, and there is
> nothing that prevents a device to reply with a buffer starting with 1
> when requested about feature 2 (because it's firmware and they just
> don't care).
> 
> This happens a lot with proprietary features on devices, when there is
> no spec, so ODM provide their own driver and they can do whatever they
> want.
> 
> If uhid or any transport layer solely takes the decision that a reply to
> a request is wrong, we have no chance of fixing it after the fact. This
> is what happens with the PS3 controller: an undocumented feature is
> used, but that's what the Playstation does, so we need to tag along.
> 
> I hope it makes more sense now.
> 
> FTR, Lee shared the logs of the issue privately, and I already told him
> where we should fix the issue.

Thanks for all the help and the insight.

I will follow-up with the suggested fixes soon.

-- 
Lee Jones [李琼斯]