[OpenMP] Fix race condition in omp_init_lock
This is a partial fix for bug 34050.
This prevents callers of omp_set_lock (which does not hold __kmp_global_lock)
from ever seeing an uninitialized version of __kmp_i_lock_table.table.
It does not solve a use-after-free race condition if omp_set_lock obtains a
pointer to __kmp_i_lock_table.table before it is updated and then attempts to
dereference afterwards. That race is far less likely and can be handled in a
separate patch.
The unit test usually segfaults on the current trunk revision. It passes with
the patch.
Patch by Adam Azarchs
Differential Revision: https://reviews.llvm.org/D39439
llvm-svn: 317115
diff --git a/openmp/runtime/src/kmp_lock.cpp b/openmp/runtime/src/kmp_lock.cpp
index bb18a6d..9c7dcaf 100644
--- a/openmp/runtime/src/kmp_lock.cpp
+++ b/openmp/runtime/src/kmp_lock.cpp
@@ -3058,11 +3058,12 @@
if (idx == __kmp_i_lock_table.size) {
// Double up the space for block pointers
int row = __kmp_i_lock_table.size / KMP_I_LOCK_CHUNK;
- kmp_indirect_lock_t **old_table = __kmp_i_lock_table.table;
- __kmp_i_lock_table.table = (kmp_indirect_lock_t **)__kmp_allocate(
+ kmp_indirect_lock_t **new_table = (kmp_indirect_lock_t **)__kmp_allocate(
2 * row * sizeof(kmp_indirect_lock_t *));
- KMP_MEMCPY(__kmp_i_lock_table.table, old_table,
+ KMP_MEMCPY(new_table, __kmp_i_lock_table.table,
row * sizeof(kmp_indirect_lock_t *));
+ kmp_indirect_lock_t **old_table = __kmp_i_lock_table.table;
+ __kmp_i_lock_table.table = new_table;
__kmp_free(old_table);
// Allocate new objects in the new blocks
for (int i = row; i < 2 * row; ++i)