[PATCH v3 2/4] platform/x86: hp-bioscfg: bound ordered-list parsing by the package count

[Muhammad Bilal <meatuni001@gmail.com>]

hp_populate_ordered_list_elements_from_package() differs from the other
per-type parsers: its main loop is bounded only by the fixed per-type
count and never checks elem against the number of elements actually
present in the package,

  for (elem = 1, eloc = 1; eloc < ORD_ELEM_CNT; elem++, eloc++)

whereas the string, integer, enumeration and password parsers bound
their main loop with "elem < count" as well.

This is safe today because hp_init_bios_package_attribute() rejects any
package with fewer than ORD_ELEM_CNT elements before the parser runs. A
later patch relaxes that check to accept shorter packages; once this
loop can be handed fewer than ORD_ELEM_CNT elements it indexes
order_obj[elem] past the end of the array - an out-of-bounds heap read.

Bound the loop by the validated element count as well, so it stops at
whichever comes first, the per-type count or the real package size,

  for (elem = 1, eloc = 1; eloc < ORD_ELEM_CNT && elem < order_obj_count;
       elem++, eloc++)

order_obj_count is the validated count plumbed in by the previous
patch. No functional change for packages that enumerate correctly
today.

Fixes: a34fc329b189 ("platform/x86: hp-bioscfg: bioscfg")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
 drivers/platform/x86/hp/hp-bioscfg/order-list-attributes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/x86/hp/hp-bioscfg/order-list-attributes.c b/drivers/platform/x86/hp/hp-bioscfg/order-list-attributes.c
index 83ddf99f93954..a50d074125268 100644
--- a/drivers/platform/x86/hp/hp-bioscfg/order-list-attributes.c
+++ b/drivers/platform/x86/hp/hp-bioscfg/order-list-attributes.c
@@ -145,7 +145,7 @@ static int hp_populate_ordered_list_elements_from_package(union acpi_object *ord
 	if (!order_obj)
 		return -EINVAL;
 
-	for (elem = 1, eloc = 1; eloc < ORD_ELEM_CNT; elem++, eloc++) {
+	for (elem = 1, eloc = 1; eloc < ORD_ELEM_CNT && elem < order_obj_count; elem++, eloc++) {
 
 		switch (order_obj[elem].type) {
 		case ACPI_TYPE_STRING:
-- 
2.55.0