Re: [PATCH 3/3] HID: asus: avoid memory leak in asus_report_fixup()

[Günther Noack]

Hello!

On Tue, Feb 17, 2026 at 07:31:23PM +0100, Benjamin Tissoires wrote:
> On Feb 17 2026, Günther Noack wrote:
> > The asus_report_fixup() function was allocating a new buffer with kmemdup()
> > when growing the report descriptor but never freeing it.  Switch to
> > devm_kzalloc() to ensure the memory is managed and freed automatically when
> > the device is removed.
> 
> Actually this one is even worse: you can't use devm_kzalloc because
> hid-core.c will later call kfree(dev->rdesc) if dev->rdesc is different
> from the one provided by the low level driver. So we are going to have
> a double free.

The buffer returned by report_fixup() is duplicated first before
hid-core stores it in dev->rdesc.  The pointer that report_fixup()
returns is not managed by the caller.

I elaborated in the response to the other patch in [1].  You can see
it in the source code in the position marked with (4).

[1] https://lore.kernel.org/all/aZTEnPEHcWEkoTJR@xxxxxxxxxx/


> I really wonder if this was ever tested.

I only convinced myself by staring at the code, because I do not
happen to have the matching USB devices here.  What it your usual
approach to verifying such changes?  raw-gadget?

—Günther