linux-kernel - Re: [PATCH] fujitsu-laptop: driver [un]registration fixes

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Message-Id: <201001051746.46942.bzolnier@gmail.com>
Date:	Tue, 5 Jan 2010 17:46:46 +0100
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Jonathan Woithe <jwoithe@...sics.adelaide.edu.au>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fujitsu-laptop: driver [un]registration fixes


Hi,

On Monday 21 December 2009 11:46:32 pm Dmitry Torokhov wrote:
> Hi Jonathan,
> 
> On Monday 21 December 2009 02:32:40 pm Jonathan Woithe wrote:
> > Hi Dmitry
> > 
> > > On Wed, Jul 29, 2009 at 10:15:33PM +0200, Bartlomiej Zolnierkiewicz wrote:
> > > > @@ -722,22 +722,22 @@ static int acpi_fujitsu_add(struct acpi_
> > > >
> > > >  	return result;
> > > >
> > > > -end:
> > > > +err_unregister_input_dev:
> > > > +	input_unregister_device(input);
> > > >  err_free_input_dev:
> > > >  	input_free_device(input);
> > > >  err_stop:
> > >
> > > Just noticed it scanning ACPI list. You must not use input_free_device()
> > > after calling input_unregister_device() since unregister likely drops the
> > > last reference to the device and it will get freed by input core.
> > 
> > So what's the correct way to deal with that in this case?  Something like
> > 
> > -end:
> > +err_unregister_input_dev:
> > +	input_unregister_device(input);
> > +	goto err_stop;
> >  err_free_input_dev:
> >  	input_free_device(input);
> >  err_stop:
> > 
> > (with a short comment to explain the goto) would circumvent the problem but
> > it looks ugly (at least to my eyes - I've never really liked "goto"s :-) ).
> 
> Just do "input = NULL;" after calling  input_unregister_device() -
> input_free_device() is like kfree() and will happily ignore passed NULL 
> pointers.
> 
> Or rearrange the code to register device last, when everything is ready.

I don't see it fixed in Linus' tree or linux-next yet so here is a patch:
(thanks for noticing the issue and sorry for the delayed reply).

[ Jonathan, please apply.  Thanks! ]

From: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Subject: [PATCH] fujitsu-laptop: fix input_free_device() usage

input_free_device() must not be used after calling input_unregister_device()
since unregister likely drops the last reference to the device and it will
get freed by input core.

Fix all input_unregister_device()+input_free_device() occurences accordingly.

Noticed-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
---
against current Linus' tree

 drivers/platform/x86/fujitsu-laptop.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

Index: b/drivers/platform/x86/fujitsu-laptop.c
===================================================================
--- a/drivers/platform/x86/fujitsu-laptop.c
+++ b/drivers/platform/x86/fujitsu-laptop.c
@@ -724,6 +724,7 @@ static int acpi_fujitsu_add(struct acpi_
 
 err_unregister_input_dev:
 	input_unregister_device(input);
+	input = NULL;
 err_free_input_dev:
 	input_free_device(input);
 err_stop:
@@ -737,8 +738,6 @@ static int acpi_fujitsu_remove(struct ac
 
 	input_unregister_device(input);
 
-	input_free_device(input);
-
 	fujitsu->acpi_handle = NULL;
 
 	return 0;
@@ -929,6 +928,7 @@ static int acpi_fujitsu_hotkey_add(struc
 
 err_unregister_input_dev:
 	input_unregister_device(input);
+	input = NULL;
 err_free_input_dev:
 	input_free_device(input);
 err_free_fifo:
@@ -952,8 +952,6 @@ static int acpi_fujitsu_hotkey_remove(st
 
 	input_unregister_device(input);
 
-	input_free_device(input);
-
 	kfifo_free(&fujitsu_hotkey->fifo);
 
 	fujitsu_hotkey->acpi_handle = NULL;

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