[PATCH] Drivers: hv: vmbus: Don't dereference ACPI root object handle

[PATCH] Drivers: hv: vmbus: Don't dereference ACPI root object handle

[Maciej S. Szmigiero]

From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>

Since the commit referenced in the Fixes: tag below the VMBus client driver
is walking the ACPI namespace up from the VMBus ACPI device to the ACPI
namespace root object trying to find Hyper-V MMIO ranges.

However, if it is not able to find them it ends trying to walk resources of
the ACPI namespace root object itself.
This object has all-ones handle, which causes a NULL pointer dereference
in the ACPI code (from dereferencing this pointer with an offset).

This in turn causes an oops on boot with VMBus host implementations that do
not provide Hyper-V MMIO ranges in their VMBus ACPI device or its
ancestors.
The QEMU VMBus implementation is an example of such implementation.

I guess providing these ranges is optional, since all tested Windows
versions seem to be able to use VMBus devices without them.

Fix this by explicitly terminating the lookup at the ACPI namespace root
object.

Note that Linux guests under KVM/QEMU do not use the Hyper-V PV interface
by default - they only do so if the KVM PV interface is missing or
disabled.

Example stack trace of such oops:
[ 3.710827] ? __die+0x1f/0x60
[ 3.715030] ? page_fault_oops+0x159/0x460
[ 3.716008] ? exc_page_fault+0x73/0x170
[ 3.716959] ? asm_exc_page_fault+0x22/0x30
[ 3.717957] ? acpi_ns_lookup+0x7a/0x4b0
[ 3.718898] ? acpi_ns_internalize_name+0x79/0xc0
[ 3.720018] acpi_ns_get_node_unlocked+0xb5/0xe0
[ 3.721120] ? acpi_ns_check_object_type+0xfe/0x200
[ 3.722285] ? acpi_rs_convert_aml_to_resource+0x37/0x6e0
[ 3.723559] ? down_timeout+0x3a/0x60
[ 3.724455] ? acpi_ns_get_node+0x3a/0x60
[ 3.725412] acpi_ns_get_node+0x3a/0x60
[ 3.726335] acpi_ns_evaluate+0x1c3/0x2c0
[ 3.727295] acpi_ut_evaluate_object+0x64/0x1b0
[ 3.728400] acpi_rs_get_method_data+0x2b/0x70
[ 3.729476] ? vmbus_platform_driver_probe+0x1d0/0x1d0 [hv_vmbus]
[ 3.730940] ? vmbus_platform_driver_probe+0x1d0/0x1d0 [hv_vmbus]
[ 3.732411] acpi_walk_resources+0x78/0xd0
[ 3.733398] vmbus_platform_driver_probe+0x9f/0x1d0 [hv_vmbus]
[ 3.734802] platform_probe+0x3d/0x90
[ 3.735684] really_probe+0x19b/0x400
[ 3.736570] ? __device_attach_driver+0x100/0x100
[ 3.737697] __driver_probe_device+0x78/0x160
[ 3.738746] driver_probe_device+0x1f/0x90
[ 3.739743] __driver_attach+0xc2/0x1b0
[ 3.740671] bus_for_each_dev+0x70/0xc0
[ 3.741601] bus_add_driver+0x10e/0x210
[ 3.742527] driver_register+0x55/0xf0
[ 3.744412] ? 0xffffffffc039a000
[ 3.745207] hv_acpi_init+0x3c/0x1000 [hv_vmbus]

Fixes: 7f163a6fd957 ("drivers:hv: Modify hv_vmbus to search for all MMIO ranges available.")
Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
---
 drivers/hv/vmbus_drv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 67f95a29aeca..edbb38f6956b 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -2287,7 +2287,8 @@ static int vmbus_acpi_add(struct platform_device *pdev)
 	 * Some ancestor of the vmbus acpi device (Gen1 or Gen2
 	 * firmware) is the VMOD that has the mmio ranges. Get that.
 	 */
-	for (ancestor = acpi_dev_parent(device); ancestor;
+	for (ancestor = acpi_dev_parent(device);
+	     ancestor && ancestor->handle != ACPI_ROOT_OBJECT;
 	     ancestor = acpi_dev_parent(ancestor)) {
 		result = acpi_walk_resources(ancestor->handle, METHOD_NAME__CRS,
 					     vmbus_walk_resources, NULL);

RE: [PATCH] Drivers: hv: vmbus: Don't dereference ACPI root object handle

[Michael Kelley (LINUX)]

From: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Sent: Wednesday, August 9, 2023 11:40 AM
> 
> Since the commit referenced in the Fixes: tag below the VMBus client driver
> is walking the ACPI namespace up from the VMBus ACPI device to the ACPI
> namespace root object trying to find Hyper-V MMIO ranges.
> 
> However, if it is not able to find them it ends trying to walk resources of
> the ACPI namespace root object itself.
> This object has all-ones handle, which causes a NULL pointer dereference
> in the ACPI code (from dereferencing this pointer with an offset).
> 
> This in turn causes an oops on boot with VMBus host implementations that do
> not provide Hyper-V MMIO ranges in their VMBus ACPI device or its
> ancestors.
> The QEMU VMBus implementation is an example of such implementation.
> 
> I guess providing these ranges is optional, since all tested Windows
> versions seem to be able to use VMBus devices without them.
> 
> Fix this by explicitly terminating the lookup at the ACPI namespace root
> object.
> 
> Note that Linux guests under KVM/QEMU do not use the Hyper-V PV interface
> by default - they only do so if the KVM PV interface is missing or
> disabled.
> 
> Example stack trace of such oops:
> [ 3.710827] ? __die+0x1f/0x60
> [ 3.715030] ? page_fault_oops+0x159/0x460
> [ 3.716008] ? exc_page_fault+0x73/0x170
> [ 3.716959] ? asm_exc_page_fault+0x22/0x30
> [ 3.717957] ? acpi_ns_lookup+0x7a/0x4b0
> [ 3.718898] ? acpi_ns_internalize_name+0x79/0xc0
> [ 3.720018] acpi_ns_get_node_unlocked+0xb5/0xe0
> [ 3.721120] ? acpi_ns_check_object_type+0xfe/0x200
> [ 3.722285] ? acpi_rs_convert_aml_to_resource+0x37/0x6e0
> [ 3.723559] ? down_timeout+0x3a/0x60
> [ 3.724455] ? acpi_ns_get_node+0x3a/0x60
> [ 3.725412] acpi_ns_get_node+0x3a/0x60
> [ 3.726335] acpi_ns_evaluate+0x1c3/0x2c0
> [ 3.727295] acpi_ut_evaluate_object+0x64/0x1b0
> [ 3.728400] acpi_rs_get_method_data+0x2b/0x70
> [ 3.729476] ? vmbus_platform_driver_probe+0x1d0/0x1d0 [hv_vmbus]
> [ 3.730940] ? vmbus_platform_driver_probe+0x1d0/0x1d0 [hv_vmbus]
> [ 3.732411] acpi_walk_resources+0x78/0xd0
> [ 3.733398] vmbus_platform_driver_probe+0x9f/0x1d0 [hv_vmbus]
> [ 3.734802] platform_probe+0x3d/0x90
> [ 3.735684] really_probe+0x19b/0x400
> [ 3.736570] ? __device_attach_driver+0x100/0x100
> [ 3.737697] __driver_probe_device+0x78/0x160
> [ 3.738746] driver_probe_device+0x1f/0x90
> [ 3.739743] __driver_attach+0xc2/0x1b0
> [ 3.740671] bus_for_each_dev+0x70/0xc0
> [ 3.741601] bus_add_driver+0x10e/0x210
> [ 3.742527] driver_register+0x55/0xf0
> [ 3.744412] ? 0xffffffffc039a000
> [ 3.745207] hv_acpi_init+0x3c/0x1000 [hv_vmbus]
> 
> Fixes: 7f163a6fd957 ("drivers:hv: Modify hv_vmbus to search for all MMIO ranges available.")
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
> ---
>  drivers/hv/vmbus_drv.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index 67f95a29aeca..edbb38f6956b 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -2287,7 +2287,8 @@ static int vmbus_acpi_add(struct platform_device *pdev)
>  	 * Some ancestor of the vmbus acpi device (Gen1 or Gen2
>  	 * firmware) is the VMOD that has the mmio ranges. Get that.
>  	 */
> -	for (ancestor = acpi_dev_parent(device); ancestor;
> +	for (ancestor = acpi_dev_parent(device);
> +	     ancestor && ancestor->handle != ACPI_ROOT_OBJECT;
>  	     ancestor = acpi_dev_parent(ancestor)) {
>  		result = acpi_walk_resources(ancestor->handle, METHOD_NAME__CRS,
>  					     vmbus_walk_resources, NULL);

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

Re: [PATCH] Drivers: hv: vmbus: Don't dereference ACPI root object handle

[Wei Liu]

On Mon, Aug 14, 2023 at 08:26:28PM +0000, Michael Kelley (LINUX) wrote:
> From: Maciej S. Szmigiero <mail@maciej.szmigiero.name> Sent: Wednesday, August 9, 2023 11:40 AM
> 
> Reviewed-by: Michael Kelley <mikelley@microsoft.com>

Applied to hyperv-next, thanks!