Overview
About vulnerability
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.
Details
- Affected product:
- Debian 10 ELS , Debian 11 ELS
- Affected packages:
- linux @ 4.19.0 (+1 more)