# Commit 9c1e8cae657bc13e8b1ddeede17603d77f3ad341
# Date 2014-06-04 11:26:15 +0200
# Author Malcolm Crossley <malcolm.crossley@citrix.com>
# Committer Jan Beulich <jbeulich@suse.com>
ACPI: Prevent acpi_table_entries from falling into a infinite loop

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

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

Based on Linux kernel commit 369d913b242cae2205471b11b6e33ac368ed33ec

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

Use < instead of <= (which I wrongly suggested), return -ENODATA
instead of -EINVAL, and make description match code.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/drivers/acpi/tables.c
+++ b/xen/drivers/acpi/tables.c
@@ -233,6 +233,12 @@ acpi_table_parse_entries(char *id,
 
 	while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <
 	       table_end) {
+		if (entry->length < sizeof(*entry)) {
+			printk(KERN_ERR PREFIX "[%4.4s:%#x] Invalid length\n",
+			       id, entry_id);
+			return -ENODATA;
+		}
+
 		if (entry->type == entry_id
 		    && (!max_entries || count++ < max_entries))
 			if (handler(entry, table_end))