mailbox: pcc: Don't access an unmapped memory address space

The acpi_pcc_probe() may end up accessing memory outside of the PCCT
table space causing the kernel panic(). Increment the pcct_entry
pointer after parsing 'HW-reduced Communications Subspace' to fix
the problem. This change also enables the parsing of subtable at
index 0.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Acked-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index ac11a9b395d3..9d3955e6ab44 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -367,8 +367,6 @@ static int __init acpi_pcc_probe(void)
                 struct acpi_generic_address *db_reg;
                 struct acpi_pcct_hw_reduced *pcct_ss;
                 pcc_mbox_channels[i].con_priv = pcct_entry;
-                pcct_entry = (struct acpi_subtable_header *)
-                        ((unsigned long) pcct_entry + pcct_entry->length);
 
                 /* If doorbell is in system memory cache the virt address */
                 pcct_ss = (struct acpi_pcct_hw_reduced *)pcct_entry;
@@ -376,6 +374,8 @@ static int __init acpi_pcc_probe(void)
                 if (db_reg->space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
                         pcc_doorbell_vaddr[i] = acpi_os_ioremap(db_reg->address,
                                                         db_reg->bit_width/8);
+                pcct_entry = (struct acpi_subtable_header *)
+                        ((unsigned long) pcct_entry + pcct_entry->length);
         }
 
         pcc_mbox_ctrl.num_chans = count;