tequilaOS/platform_hardware_interfaces
2
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity

Fix strict weak ordering requirement of less than operation

Browse source 
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
This commit is contained in:
Janis Danisevskis 2018-06-17 14:06:20 -07:00
parent 9c9fea329e
commit 93c7276e3a
1 changed files with 3 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
keymaster/4.0/support/keymaster_utils.cpp
View file

@ -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>