6.4-stable review patch. If anyone has any objections, please let me know.
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From: Maciej S. Szmigiero maciej.szmigiero@oracle.com
[ Upstream commit 78e04bbff849b51b56f5925b1945db2c6e128b61 ]
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 Reviewed-by: Michael Kelley mikelley@microsoft.com Signed-off-by: Wei Liu wei.liu@kernel.org Link: https://lore.kernel.org/r/fd8e64ceeecfd1d95ff49021080cf699e88dbbde.169160626... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 67f95a29aeca5..edbb38f6956b9 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);