Re: [PATCH v2 13/27] mfd: twl-core: Clear twl_priv pointer on teardown and probe failure

[Andreas Kemnade]

On Fri, 30 Oct 2026 11:28:35 +0000
Lee Jones <lee@xxxxxxxxxx> wrote:

> On Fri, 30 Oct 2026, Andreas Kemnade wrote:
> 
> > On Fri, 30 Oct 2026 10:48:06 +0000
> > Lee Jones <lee@xxxxxxxxxx> wrote:
> >   
> > > On Wed, 28 Oct 2026, Andreas Kemnade wrote:
> > >   
> > > > On Tue, 27 Oct 2026 09:30:42 +0000
> > > > Lee Jones <lee@xxxxxxxxxx> wrote:
> > > >     
> > > > > twl_probe() allocates the file-scope twl_priv state with devm_kzalloc()
> > > > > and checks for a non-NULL twl_priv at entry to reject multiple device
> > > > > instances.  However, twl_remove() and the early error paths in
> > > > > twl_probe() never reset twl_priv to NULL, a failure when adding MFD
> > > > > child devices bypasses twl_remove() by jumping to free instead of fail,
> > > > > and twl_remove() tears down the IRQ domain and dummy I2C clients before
> > > > > child devices are unregistered.  After devres frees the underlying
> > > > > memory on probe failure or unbind, twl_priv remains a dangling pointer,
> > > > > causing subsequent exported API calls to dereference freed memory and
> > > > > blocking future probe attempts with -EBUSY.
> > > > > 
> > > > > Unregister DT-populated and MFD child devices at the start of
> > > > > twl_remove(), ensure mfd_add_devices() failures unwind via fail, and
> > > > > reset twl_priv to NULL in twl_remove() and on probe error exit.
> > > > > 
> > > > > Fixes: 80a97ccd33be ("mfd: twl-core: Collect global variables behind one private structure (global)")
> > > > > Closes: https://sashiko.dev/#/bug/linux-73e82f84-94de-4d08-82a4-f22d42a1dedf
> > > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > > Signed-off-by: Lee Jones <lee@xxxxxxxxxx>    
> > > > 
> > > > Hmm, couldn't we use devm_add_action_or_reset() for resetting the
> > > > twl_priv pointer? Feels more clean for me.    
> > > 
> > > Nice!  Thanks for the suggestion.
> > > 
> > > To keep this fix minimal for Stable backporting (and avoid resending a
> > > 27-patch series), I'll take this one as-is and send a follow-up patch
> > > converting twl_priv to use devm_add_action_or_reset().
> > >   
> > 
> > I think the whole patch can be simplified a lot then, 
> > 
> > devm_mfd_add_devices can stay.  
> 
> twl_remove() runs before devres teardown and destroys the IRQ domain,
> unregisters the dummy I2C clients and clears twl_priv->ready.
> 
> So the MFD child devices still need to be unregistered at the start of
> twl_remove() (alongside of_platform_depopulate()) before the parent
> transport is torn down beneath them, at least until the rest of
> twl_remove() is also converted to devm_*().
> 

ok, I merged the two chunks of twl_remove() into one in my head without
the lines in between... So you are right.

Regards,
Andreas