linux-kernel - RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

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Date:   Sat, 30 Jan 2021 03:55:13 +0000
From:   "Yuan, Perry" <Perry.Yuan@...l.com>
To:     "Limonciello, Mario" <Mario.Limonciello@...l.com>,
        Hans De Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>
CC:     LKML <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "Bharathi, Divya" <Divya.Bharathi@...l.com>,
        "Ksr, Prasanth" <Prasanth.Ksr@...l.com>,
        "Martinez3, Juan" <Juan.Martinez@...l.com>,
        "Wang, David D" <David.D.Wang@...l.com>
Subject: RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
 dereference

> -----Original Message-----
> From: Limonciello, Mario <Mario_Limonciello@...l.com>
> Sent: 2021年1月30日 1:29
> To: Hans De Goede; Mark Gross
> Cc: LKML; platform-driver-x86@...r.kernel.org; Bharathi, Divya; Ksr, Prasanth;
> Yuan, Perry
> Subject: RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
> dereference
> 
> +Divya, +Prasanth, +Perry
> 
> > -----Original Message-----
> > From: Limonciello, Mario <Mario_Limonciello@...l.com>
> > Sent: Friday, January 29, 2021 11:27
> > To: Hans De Goede; Mark Gross
> > Cc: LKML; platform-driver-x86@...r.kernel.org; Limonciello, Mario
> > Subject: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
> > dereference
> >
> > An upcoming Dell platform is causing a NULL pointer dereference in
> > dell-wmi-sysman initialization.  Validate that the input from BIOS
> > matches correct ACPI types and abort module initialization if it
> > fails.
> >
> > This leads to a memory leak that needs to be cleaned up properly.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
> > ---
> >  drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > index dc6dd531c996..38b497991071 100644
> > --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type,
> > const char *guid)
> >  		return retval;
> >  	/* need to use specific instance_id and guid combination to get
> > right data */
> >  	obj = get_wmiobj_pointer(instance_id, guid);
> > -	if (!obj)
> > +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> > +		release_attributes_data();
> >  		return -ENODEV;
> > +	}
> >  	elements = obj->package.elements;
> >
> >  	mutex_lock(&wmi_priv.mutex);
> >  	while (elements) {
> >  		/* sanity checking */
> > +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
> > +			pr_debug("incorrect element type\n");
> > +			goto nextobj;
> > +		}
> >  		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
> >  			pr_debug("empty attribute found\n");
> >  			goto nextobj;
> > --
> > 2.25.1

Tested on the Dell laptop system which I found the issue. 
Kernel can boot up with this new fix patch without any panic triggered.

Tested-by: Perry Yuan <perry_yuan@...l.com>