4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Erik Schmauss <[email protected]>

[ Upstream commit f016b19a9275089a2ab06c2144567c2ad8d5d6ad ]

The value coming from acpi_hw_read() should not be used if it
returns an error code, so check the status returned by it before
using that value in two places in acpi_hw_register_read().

Reported-by: Mark Gross <[email protected]>
Signed-off-by: Erik Schmauss <[email protected]>
[ rjw: Changelog ]
Signed-off-by: Rafael J. Wysocki <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/acpi/acpica/hwregs.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/acpi/acpica/hwregs.c
+++ b/drivers/acpi/acpica/hwregs.c
@@ -528,13 +528,18 @@ acpi_status acpi_hw_register_read(u32 re
 
                status =
                    acpi_hw_read(&value64, &acpi_gbl_FADT.xpm2_control_block);
-               value = (u32)value64;
+               if (ACPI_SUCCESS(status)) {
+                       value = (u32)value64;
+               }
                break;
 
        case ACPI_REGISTER_PM_TIMER:    /* 32-bit access */
 
                status = acpi_hw_read(&value64, &acpi_gbl_FADT.xpm_timer_block);
-               value = (u32)value64;
+               if (ACPI_SUCCESS(status)) {
+                       value = (u32)value64;
+               }
+
                break;
 
        case ACPI_REGISTER_SMI_COMMAND_BLOCK:   /* 8-bit access */


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