In the Linux kernel, the following vulnerability has been resolved: platform/x86: hp-bioscfg: pass validated element count to package parse

In the Linux kernel, the following vulnerability has been resolved:

platform/x86: hp-bioscfg: pass validated element count to package parsers

The per-type package parsers are handed the wrong element count.

hp_init_bios_package_attribute() validates obj->package.count and then
calls one of the five hp_populate_package_data() wrappers (string,
integer, enumeration, ordered list, password). Each wrapper forwards a
count to its hp_populate_elements_from_package() parser, but instead
of forwarding the validated obj->package.count it derives the count
from elements[0]. elements[0] is the NAME field and is always an
ACPI_TYPE_STRING, so reading ->package.count from it in fact reads
->string.length through the union acpi_object. The parsers thus bound
themselves against the length of the name string rather than against
the real number of elements in the package.

This is safe today because hp_init_bios_package_attribute() refuses any
package that has fewer than the type's element count, so a parser only
ever runs on a full package and never reads past it regardless of the
bogus bound.

An upcoming change relaxes that check to accept shorter packages. Once
a parser can receive fewer elements than its per-type count, a bound
taken from the name length no longer reflects the array size, and the
"elem < count" loop conditions and "elem + n >= count" sub-loop guards
read past the end of elements[] - an out-of-bounds heap read.

Forward the validated obj->package.count to every *_package_data()
wrapper so the parsers bound themselves against the real package size.
This does not change behaviour for the packages that enumerate
correctly today and is a prerequisite for accepting shorter packages
safely.