RE: [PATCH v7 net-next 2/8] dpll: allow registering FW-identified pin with a different DPLL

[Nitka, Grzegorz]

> -----Original Message-----
> From: Jakub Kicinski <kuba@xxxxxxxxxx>
> Sent: Saturday, May 2, 2026 7:27 PM
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> Loktionov, Aleksandr <aleksandr.loktionov@xxxxxxxxx>
> Subject: Re: [PATCH v7 net-next 2/8] dpll: allow registering FW-identified pin
> with a different DPLL
> 
> On Thu, 30 Apr 2026 11:42:32 +0200 Grzegorz Nitka wrote:
> > Relax the (module, clock_id) equality requirement when registering a
> > pin identified by firmware (pin->fwnode). Some platforms associate a
> > FW-described pin with a DPLL instance that differs from the pin's
> > (module, clock_id) tuple. For such pins, permit registration without
> > requiring the strict match. Non-FW pins still require equality.
> 
> AI asks what prevents the modules from disappearing:
> 
> Does this relaxed check expose pin->module to a use-after-free during
> netlink queries?
> If module A registers a firmware-described pin allocated by module B,
> they will have different module pointers.
> Because fwnode_dpll_pin_find() increases the pin's refcount but does
> not take a reference to module B via try_module_get(), it appears module B
> could be unloaded while module A still holds an active reference to the pin.
> When module B unloads, its struct module memory is freed, leaving
> pin->module as a dangling pointer.
> A subsequent user-space Netlink query using DPLL_CMD_PIN_GET iterates
> over
> the registered pins and calls nla_put_string() with module_name(pin-
> >module),
> which would dereference the freed module memory.

This AI review comment is a valid concern.
I'm going, of course, to address it in the next iteration.

Thanks

Grzegorz