pci/dmar: correct off-by-one error in dmar_fault()

DMAR faults are recorded into a ring of "fault recording registers".
fault_index is a 0-based index into the ring. The code allows the
0-based fault_index to be equal to the total number of fault registers
available from the cap_num_fault_regs() macro, which causes access
beyond the last available register.

Signed-off-by Troy Heber <troy.heber@hp.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/drivers/pci/dmar.c b/drivers/pci/dmar.c
index 380b60e..3264b62 100644 (file)
--- a/drivers/pci/dmar.c
+++ b/drivers/pci/dmar.c
@@ -1226,7 +1226,7 @@ irqreturn_t dmar_fault(int irq, void *dev_id)
                                source_id, guest_addr);
 
                fault_index++;
-               if (fault_index > cap_num_fault_regs(iommu->cap))
+               if (fault_index >= cap_num_fault_regs(iommu->cap))
                        fault_index = 0;
                spin_lock_irqsave(&iommu->register_lock, flag);
        }