Commit 93c7276e authored Jun 17, 2018 by Janis Danisevskis

Fix strict weak ordering requirement of less than operation

operator< on hidl_vec<uint8_t> violates strict weak ordering in the case
that one oparand is shorter that the other and the shorter is a prefix
of the longer.

if x and y are incomparable, i.e., neither x < y nor y < x and
   y and z are incomparable, i.e., neither y < z nor z < y, then
   x and z must be incomparable.
As for the current implementation the first two statements are true but
the third is not given the following example input:
x:="aa", y:="a", z:="ab".

This patch fixes the issue by defining a < b if a is a prefix of b.

As this relation is used in a std::sort algorithm which demands strict
weak ordering this bug leads to undefined behavior.

Change-Id: I4961bb35e2fd4f5fcf561ec0c7c536f81830aab8

parent 9c9fea32

keymaster/4.0/support/keymaster_utils.cpp

+3 −1

Original line number	Diff line number	Diff line
		@@ -21,7 +21,9 @@ namespace android {
		namespace hardware {

		inline static bool operator<(const hidl_vec<uint8_t>& a, const hidl_vec<uint8_t>& b) {
		return memcmp(a.data(), b.data(), std::min(a.size(), b.size())) == -1;
		auto result = memcmp(a.data(), b.data(), std::min(a.size(), b.size()));
		if (!result) return a.size() < b.size();
		return result < 0;
		}

		template <size_t SIZE>