iommu/amd: Do proper access checking before calling handle_mm_fault()

The handle_mm_fault function expects the caller to do the
access checks. Not doing so and calling the function with
wrong permissions is a bug (catched by a BUG_ON).
So fix this bug by adding proper access checking to the io
page-fault code in the AMD IOMMUv2 driver.

Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-By: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/amd_iommu_v2.c b/drivers/iommu/amd_iommu_v2.c
index d21d4ed..7caf2fa 100644 (file)
--- a/drivers/iommu/amd_iommu_v2.c
+++ b/drivers/iommu/amd_iommu_v2.c
@@ -494,6 +494,22 @@ static void handle_fault_error(struct fault *fault)
        }
 }
 
+static bool access_error(struct vm_area_struct *vma, struct fault *fault)
+{
+       unsigned long requested = 0;
+
+       if (fault->flags & PPR_FAULT_EXEC)
+               requested |= VM_EXEC;
+
+       if (fault->flags & PPR_FAULT_READ)
+               requested |= VM_READ;
+
+       if (fault->flags & PPR_FAULT_WRITE)
+               requested |= VM_WRITE;
+
+       return (requested & ~vma->vm_flags) != 0;
+}
+
 static void do_fault(struct work_struct *work)
 {
        struct fault *fault = container_of(work, struct fault, work);
@@ -516,8 +532,8 @@ static void do_fault(struct work_struct *work)
                goto out;
        }
 
-       if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) {
-               /* handle_mm_fault would BUG_ON() */
+       /* Check if we have the right permissions on the vma */
+       if (access_error(vma, fault)) {
                up_read(&mm->mmap_sem);
                handle_fault_error(fault);
                goto out;