Re: [Xen-devel] Xen 4.0.0-rc7 problem/hang with vt-d DMAR parsing

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> Weidong Han <weidong.han@xxxxxxxxx> 25.03.10 01:55 >>>
>Do you mean to know which case fails on length checking? How about below 
>patch?

Yes, something like this. Although I'd prefer to have a general
sizeof(struct acpi_dmar_entry_header) check before the switch
statement (to avoid even looking at out of range header fields),
and "break"s instead of "goto disable"s.

Jan

diff -r a4eac162dcb9 xen/drivers/passthrough/vtd/dmar.c
--- a/xen/drivers/passthrough/vtd/dmar.c    Thu Mar 25 01:05:03 2010 +0800
+++ b/xen/drivers/passthrough/vtd/dmar.c    Thu Mar 25 17:46:03 2010 +0800
@@ -664,21 +664,57 @@ static int __init acpi_parse_dmar(struct
         case ACPI_DMAR_DRHD:
             if ( iommu_verbose )
                 dprintk(VTDPREFIX, "found ACPI_DMAR_DRHD:\n");
+
+            if ( entry_header->length < sizeof(struct acpi_table_drhd) )
+            {
+                dprintk(XENLOG_ERR VTDPREFIX,
+                        "  Invalid length: 0x%x\n", entry_header->length);
+                ret = -EINVAL;
+                goto disable;
+            }
+
             ret = acpi_parse_one_drhd(entry_header);
             break;
         case ACPI_DMAR_RMRR:
             if ( iommu_verbose )
                 dprintk(VTDPREFIX, "found ACPI_DMAR_RMRR:\n");
+
+            if ( entry_header->length < sizeof(struct acpi_table_rmrr) )
+            {
+                dprintk(XENLOG_ERR VTDPREFIX,
+                        "  Invalid length: 0x%x\n", entry_header->length);
+                ret = -EINVAL;
+                goto disable;
+            }
+
             ret = acpi_parse_one_rmrr(entry_header);
             break;
         case ACPI_DMAR_ATSR:
             if ( iommu_verbose )
                 dprintk(VTDPREFIX, "found ACPI_DMAR_ATSR:\n");
+
+            if ( entry_header->length < sizeof(struct acpi_table_atsr) )
+            {
+                dprintk(XENLOG_ERR VTDPREFIX,
+                        "  Invalid length: 0x%x\n", entry_header->length);
+                ret = -EINVAL;
+                goto disable;
+            }
+
             ret = acpi_parse_one_atsr(entry_header);
             break;
         case ACPI_DMAR_RHSA:
             if ( iommu_verbose )
                 dprintk(VTDPREFIX, "found ACPI_DMAR_RHSA:\n");
+
+            if ( entry_header->length < sizeof(struct acpi_table_rhsa) )
+            {
+                dprintk(XENLOG_ERR VTDPREFIX,
+                        "  Invalid length: 0x%x\n", entry_header->length);
+                ret = -EINVAL;
+                goto disable;
+            }
+
             ret = acpi_parse_one_rhsa(entry_header);
             break;
         default:
@@ -694,6 +730,7 @@ static int __init acpi_parse_dmar(struct
         entry_header = ((void *)entry_header + entry_header->length);
     }

+disable:
     if ( ret )
     {
         printk(XENLOG_WARNING



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