[Xen-devel] [PATCH v2] xen/acpi: off by one in read_acpi_id()

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

If acpi_id is == nr_acpi_bits, then we access one element beyond the end
of the acpi_psd[] array or we set one bit beyond the end of the bit map
when we do __set_bit(acpi_id, acpi_id_present);

Fixes: 59a568029181 ("xen/acpi-processor: C and P-state driver that uploads 
said data to hypervisor.")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Reviewed-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>

diff --git a/drivers/xen/xen-acpi-processor.c b/drivers/xen/xen-acpi-processor.c
index c80195e8fbd1..b29f4e40851f 100644
--- a/drivers/xen/xen-acpi-processor.c
+++ b/drivers/xen/xen-acpi-processor.c
@@ -364,9 +364,9 @@ read_acpi_id(acpi_handle handle, u32 lvl, void *context, 
void **rv)
        }
        /* There are more ACPI Processor objects than in x2APIC or MADT.
         * This can happen with incorrect ACPI SSDT declerations. */
-       if (acpi_id > nr_acpi_bits) {
-               pr_debug("We only have %u, trying to set %u\n",
-                        nr_acpi_bits, acpi_id);
+       if (acpi_id >= nr_acpi_bits) {
+               pr_debug("max acpi id %u, trying to set %u\n",
+                        nr_acpi_bits - 1, acpi_id);
                return AE_OK;
        }
        /* OK, There is a ACPI Processor object */

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