[Xen-devel] [PATCH] ACPI: Prevent acpi_table_entries from falling into a infinite loop

[Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>]

If a buggy BIOS programs an ACPI table with entry length 0 then
acpi_table_entries gets stuck in an infinite loop.

To aid debugging, report the error and exit the loop.

Signed-off-by: Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>

diff -r 4708591d8aa8 -r af3b2493951c xen/drivers/acpi/tables.c
--- a/xen/drivers/acpi/tables.c
+++ b/xen/drivers/acpi/tables.c
@@ -238,6 +238,12 @@ acpi_table_parse_entries(char *id,
                        if (handler(entry, table_end))
                                return -EINVAL;
 
+               if (entry->length == 0) {
+                       printk(KERN_ERR PREFIX "[%4.4s:0x%02x] Invalid zero 
length\n",
+                              id, entry_id);
+                       return -EINVAL;
+               }
+
                entry = (struct acpi_subtable_header *)
                    ((unsigned long)entry + entry->length);
        }

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