[PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Takashi Iwai]

intel_dsm_platform_mux_info() tries to parse the ACPI package data
from _DSM for the debug information, but it assumes the fixed format
without checking what values are stored in the elements actually.
When an unexpected value is returned from BIOS, it may lead to GPF or
NULL dereference, as reported recently.

Add the checks of the contents in the returned values and skip the
values for invalid cases.

v1->v2: Check the info contents before dereferencing, too

BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 drivers/gpu/drm/i915/display/intel_acpi.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
index e21fb14d5e07..833d0c1be4f1 100644
--- a/drivers/gpu/drm/i915/display/intel_acpi.c
+++ b/drivers/gpu/drm/i915/display/intel_acpi.c
@@ -84,13 +84,31 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
 		return;
 	}
 
+	if (!pkg->package.count) {
+		DRM_DEBUG_DRIVER("no connection in _DSM\n");
+		return;
+	}
+
 	connector_count = &pkg->package.elements[0];
 	DRM_DEBUG_DRIVER("MUX info connectors: %lld\n",
 		  (unsigned long long)connector_count->integer.value);
 	for (i = 1; i < pkg->package.count; i++) {
 		union acpi_object *obj = &pkg->package.elements[i];
-		union acpi_object *connector_id = &obj->package.elements[0];
-		union acpi_object *info = &obj->package.elements[1];
+		union acpi_object *connector_id;
+		union acpi_object *info;
+
+		if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2) {
+			DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
+			continue;
+		}
+
+		connector_id = &obj->package.elements[0];
+		info = &obj->package.elements[1];
+		if (info->type != ACPI_TYPE_BUFFER || info->buffer.length < 4) {
+			DRM_DEBUG_DRIVER("Invalid info for MUX obj #%d\n", i);
+			continue;
+		}
+
 		DRM_DEBUG_DRIVER("Connector id: 0x%016llx\n",
 			  (unsigned long long)connector_id->integer.value);
 		DRM_DEBUG_DRIVER("  port id: %s\n",
-- 
2.26.2

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Ville Syrjälä]

On Fri, Apr 02, 2021 at 10:23:17AM +0200, Takashi Iwai wrote:
> intel_dsm_platform_mux_info() tries to parse the ACPI package data
> from _DSM for the debug information, but it assumes the fixed format
> without checking what values are stored in the elements actually.
> When an unexpected value is returned from BIOS, it may lead to GPF or
> NULL dereference, as reported recently.
> 
> Add the checks of the contents in the returned values and skip the
> values for invalid cases.
> 
> v1->v2: Check the info contents before dereferencing, too
> 
> BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
>  drivers/gpu/drm/i915/display/intel_acpi.c | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> index e21fb14d5e07..833d0c1be4f1 100644
> --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> @@ -84,13 +84,31 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
>  		return;
>  	}
>  
> +	if (!pkg->package.count) {
> +		DRM_DEBUG_DRIVER("no connection in _DSM\n");
> +		return;
> +	}
> +
>  	connector_count = &pkg->package.elements[0];
>  	DRM_DEBUG_DRIVER("MUX info connectors: %lld\n",
>  		  (unsigned long long)connector_count->integer.value);
>  	for (i = 1; i < pkg->package.count; i++) {
>  		union acpi_object *obj = &pkg->package.elements[i];
> -		union acpi_object *connector_id = &obj->package.elements[0];
> -		union acpi_object *info = &obj->package.elements[1];
> +		union acpi_object *connector_id;
> +		union acpi_object *info;
> +
> +		if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2) {
> +			DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
> +			continue;
> +		}
> +
> +		connector_id = &obj->package.elements[0];

You don't want to check connector_id->type as well?

> +		info = &obj->package.elements[1];
> +		if (info->type != ACPI_TYPE_BUFFER || info->buffer.length < 4) {
> +			DRM_DEBUG_DRIVER("Invalid info for MUX obj #%d\n", i);
> +			continue;
> +		}
> +
>  		DRM_DEBUG_DRIVER("Connector id: 0x%016llx\n",
>  			  (unsigned long long)connector_id->integer.value);
>  		DRM_DEBUG_DRIVER("  port id: %s\n",
> -- 
> 2.26.2
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Takashi Iwai]

On Wed, 07 Apr 2021 18:34:46 +0200,
Ville Syrjälä wrote:
> 
> On Fri, Apr 02, 2021 at 10:23:17AM +0200, Takashi Iwai wrote:
> > intel_dsm_platform_mux_info() tries to parse the ACPI package data
> > from _DSM for the debug information, but it assumes the fixed format
> > without checking what values are stored in the elements actually.
> > When an unexpected value is returned from BIOS, it may lead to GPF or
> > NULL dereference, as reported recently.
> > 
> > Add the checks of the contents in the returned values and skip the
> > values for invalid cases.
> > 
> > v1->v2: Check the info contents before dereferencing, too
> > 
> > BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > ---
> >  drivers/gpu/drm/i915/display/intel_acpi.c | 22 ++++++++++++++++++++--
> >  1 file changed, 20 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> > index e21fb14d5e07..833d0c1be4f1 100644
> > --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> > +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> > @@ -84,13 +84,31 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
> >  		return;
> >  	}
> >  
> > +	if (!pkg->package.count) {
> > +		DRM_DEBUG_DRIVER("no connection in _DSM\n");
> > +		return;
> > +	}
> > +
> >  	connector_count = &pkg->package.elements[0];
> >  	DRM_DEBUG_DRIVER("MUX info connectors: %lld\n",
> >  		  (unsigned long long)connector_count->integer.value);
> >  	for (i = 1; i < pkg->package.count; i++) {
> >  		union acpi_object *obj = &pkg->package.elements[i];
> > -		union acpi_object *connector_id = &obj->package.elements[0];
> > -		union acpi_object *info = &obj->package.elements[1];
> > +		union acpi_object *connector_id;
> > +		union acpi_object *info;
> > +
> > +		if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2) {
> > +			DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
> > +			continue;
> > +		}
> > +
> > +		connector_id = &obj->package.elements[0];
> 
> You don't want to check connector_id->type as well?

I added only the minimal checks that may lead to Oops.


Takashi

> 
> > +		info = &obj->package.elements[1];
> > +		if (info->type != ACPI_TYPE_BUFFER || info->buffer.length < 4) {
> > +			DRM_DEBUG_DRIVER("Invalid info for MUX obj #%d\n", i);
> > +			continue;
> > +		}
> > +
> >  		DRM_DEBUG_DRIVER("Connector id: 0x%016llx\n",
> >  			  (unsigned long long)connector_id->integer.value);
> >  		DRM_DEBUG_DRIVER("  port id: %s\n",
> > -- 
> > 2.26.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel
> 

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Ville Syrjälä]

On Wed, Apr 07, 2021 at 06:56:15PM +0200, Takashi Iwai wrote:
> On Wed, 07 Apr 2021 18:34:46 +0200,
> Ville Syrjälä wrote:
> > 
> > On Fri, Apr 02, 2021 at 10:23:17AM +0200, Takashi Iwai wrote:
> > > intel_dsm_platform_mux_info() tries to parse the ACPI package data
> > > from _DSM for the debug information, but it assumes the fixed format
> > > without checking what values are stored in the elements actually.
> > > When an unexpected value is returned from BIOS, it may lead to GPF or
> > > NULL dereference, as reported recently.
> > > 
> > > Add the checks of the contents in the returned values and skip the
> > > values for invalid cases.
> > > 
> > > v1->v2: Check the info contents before dereferencing, too
> > > 
> > > BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
> > > Cc: <stable@vger.kernel.org>
> > > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_acpi.c | 22 ++++++++++++++++++++--
> > >  1 file changed, 20 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> > > index e21fb14d5e07..833d0c1be4f1 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> > > @@ -84,13 +84,31 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
> > >  		return;
> > >  	}
> > >  
> > > +	if (!pkg->package.count) {
> > > +		DRM_DEBUG_DRIVER("no connection in _DSM\n");
> > > +		return;
> > > +	}
> > > +
> > >  	connector_count = &pkg->package.elements[0];
> > >  	DRM_DEBUG_DRIVER("MUX info connectors: %lld\n",
> > >  		  (unsigned long long)connector_count->integer.value);
> > >  	for (i = 1; i < pkg->package.count; i++) {
> > >  		union acpi_object *obj = &pkg->package.elements[i];
> > > -		union acpi_object *connector_id = &obj->package.elements[0];
> > > -		union acpi_object *info = &obj->package.elements[1];
> > > +		union acpi_object *connector_id;
> > > +		union acpi_object *info;
> > > +
> > > +		if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2) {
> > > +			DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
> > > +			continue;
> > > +		}
> > > +
> > > +		connector_id = &obj->package.elements[0];
> > 
> > You don't want to check connector_id->type as well?
> 
> I added only the minimal checks that may lead to Oops.

OK. I guess misinterpreting something else as an integer isn't
particular dangerous in this case.

Pushed to drm-intel-next. Thanks.

Oh, could you ask the bug reporter to attach an acpidump to the
bug? Might be good to have that stuff on record somewhere if/when
someone wants to actually figure out what's going on here.

That said, maybe we should just nuke this whole thing instead?
Unless I'm missing someting this code doesn't seem to actually
do anything...

-- 
Ville Syrjälä
Intel

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Takashi Iwai]

On Wed, 07 Apr 2021 23:28:48 +0200,
Ville Syrjälä wrote:
> 
> On Wed, Apr 07, 2021 at 06:56:15PM +0200, Takashi Iwai wrote:
> > On Wed, 07 Apr 2021 18:34:46 +0200,
> > Ville Syrjälä wrote:
> > > 
> > > On Fri, Apr 02, 2021 at 10:23:17AM +0200, Takashi Iwai wrote:
> > > > intel_dsm_platform_mux_info() tries to parse the ACPI package data
> > > > from _DSM for the debug information, but it assumes the fixed format
> > > > without checking what values are stored in the elements actually.
> > > > When an unexpected value is returned from BIOS, it may lead to GPF or
> > > > NULL dereference, as reported recently.
> > > > 
> > > > Add the checks of the contents in the returned values and skip the
> > > > values for invalid cases.
> > > > 
> > > > v1->v2: Check the info contents before dereferencing, too
> > > > 
> > > > BugLink: http://bugzilla.opensuse.org/show_bug.cgi?id=1184074
> > > > Cc: <stable@vger.kernel.org>
> > > > Signed-off-by: Takashi Iwai <tiwai@suse.de>
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_acpi.c | 22 ++++++++++++++++++++--
> > > >  1 file changed, 20 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_acpi.c b/drivers/gpu/drm/i915/display/intel_acpi.c
> > > > index e21fb14d5e07..833d0c1be4f1 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_acpi.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_acpi.c
> > > > @@ -84,13 +84,31 @@ static void intel_dsm_platform_mux_info(acpi_handle dhandle)
> > > >  		return;
> > > >  	}
> > > >  
> > > > +	if (!pkg->package.count) {
> > > > +		DRM_DEBUG_DRIVER("no connection in _DSM\n");
> > > > +		return;
> > > > +	}
> > > > +
> > > >  	connector_count = &pkg->package.elements[0];
> > > >  	DRM_DEBUG_DRIVER("MUX info connectors: %lld\n",
> > > >  		  (unsigned long long)connector_count->integer.value);
> > > >  	for (i = 1; i < pkg->package.count; i++) {
> > > >  		union acpi_object *obj = &pkg->package.elements[i];
> > > > -		union acpi_object *connector_id = &obj->package.elements[0];
> > > > -		union acpi_object *info = &obj->package.elements[1];
> > > > +		union acpi_object *connector_id;
> > > > +		union acpi_object *info;
> > > > +
> > > > +		if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count < 2) {
> > > > +			DRM_DEBUG_DRIVER("Invalid object for MUX #%d\n", i);
> > > > +			continue;
> > > > +		}
> > > > +
> > > > +		connector_id = &obj->package.elements[0];
> > > 
> > > You don't want to check connector_id->type as well?
> > 
> > I added only the minimal checks that may lead to Oops.
> 
> OK. I guess misinterpreting something else as an integer isn't
> particular dangerous in this case.
> 
> Pushed to drm-intel-next. Thanks.

Great, thanks!

> Oh, could you ask the bug reporter to attach an acpidump to the
> bug? Might be good to have that stuff on record somewhere if/when
> someone wants to actually figure out what's going on here.

OK, I'll ask.

> That said, maybe we should just nuke this whole thing instead?
> Unless I'm missing someting this code doesn't seem to actually
> do anything...

Yeah, that looks nothing but showing the debug information and that
can be checked via acpidump output, too...


Takashi

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Takashi Iwai]

On Thu, 08 Apr 2021 09:51:18 +0200,
Takashi Iwai wrote:
> 
> On Wed, 07 Apr 2021 23:28:48 +0200,
> Ville Syrjälä wrote:
> > 
> > Oh, could you ask the bug reporter to attach an acpidump to the
> > bug? Might be good to have that stuff on record somewhere if/when
> > someone wants to actually figure out what's going on here.
> 
> OK, I'll ask.

Available at
  acpidump: https://susepaste.org/59777448
  hwinfo: https://susepaste.org/86284020


thanks,

Takashi

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Ville Syrjälä]

On Thu, Apr 08, 2021 at 06:34:06PM +0200, Takashi Iwai wrote:
> On Thu, 08 Apr 2021 09:51:18 +0200,
> Takashi Iwai wrote:
> > 
> > On Wed, 07 Apr 2021 23:28:48 +0200,
> > Ville Syrjälä wrote:
> > > 
> > > Oh, could you ask the bug reporter to attach an acpidump to the
> > > bug? Might be good to have that stuff on record somewhere if/when
> > > someone wants to actually figure out what's going on here.
> > 
> > OK, I'll ask.
> 
> Available at
>   acpidump: https://susepaste.org/59777448
>   hwinfo: https://susepaste.org/86284020

Those will apparently expire real soon. I took local copies out
of morbid curiosity, but that's not going to help anyone else 
in the future. I rather wish bug reporting tools would flat out
refuse to accept any pastebin links.

-- 
Ville Syrjälä
Intel

Re: [Intel-gfx] [PATCH v2] drm/i915: Fix invalid access to ACPI _DSM objects

[Takashi Iwai]

On Thu, 08 Apr 2021 18:56:06 +0200,
Ville Syrjälä wrote:
> 
> On Thu, Apr 08, 2021 at 06:34:06PM +0200, Takashi Iwai wrote:
> > On Thu, 08 Apr 2021 09:51:18 +0200,
> > Takashi Iwai wrote:
> > > 
> > > On Wed, 07 Apr 2021 23:28:48 +0200,
> > > Ville Syrjälä wrote:
> > > > 
> > > > Oh, could you ask the bug reporter to attach an acpidump to the
> > > > bug? Might be good to have that stuff on record somewhere if/when
> > > > someone wants to actually figure out what's going on here.
> > > 
> > > OK, I'll ask.
> > 
> > Available at
> >   acpidump: https://susepaste.org/59777448
> >   hwinfo: https://susepaste.org/86284020
> 
> Those will apparently expire real soon. I took local copies out
> of morbid curiosity, but that's not going to help anyone else 
> in the future. I rather wish bug reporting tools would flat out
> refuse to accept any pastebin links.

Yeah, don't worry, I'll upload them to Bugzilla later in anyway.


Takashi