[Tagged Pointers] Allow probing the current TP level w/ locking.
aosp/1484976 introduced a breaking change where
DisableMemoryMitigations() now indiscriminately turns tagged pointers
off. When android_mallopt(M_DISABLE_MEMORY_MITIGATIONS) is called, the
correct behaviour is:
- In SYNC/ASYNC MTE mode -> disable all tagged pointers.
- If all tagged pointers are already disabled -> nop.
- If we're in TBI mode -> nop (keep the TBI mode as-is).
In order to do that we have to allow probing of the current heap tagging
mode. In order to prevent TOCTOU between GetHeapTaggingLevel() and
SetHeapTaggingLevel(), we expose a global mutex that should be held when
calling these functions.
Bug: 174263432
Test: atest CtsTaggingHostTestCases on Flame
Change-Id: Ia96f7269d542c9041270458806aee36766d2fbbb
diff --git a/libc/bionic/malloc_common_dynamic.cpp b/libc/bionic/malloc_common_dynamic.cpp
index eeeaff9..2d6a1bb 100644
--- a/libc/bionic/malloc_common_dynamic.cpp
+++ b/libc/bionic/malloc_common_dynamic.cpp
@@ -58,6 +58,7 @@
#include <android/dlext.h>
#include <platform/bionic/malloc.h>
+#include <private/ScopedPthreadMutexLocker.h>
#include <private/bionic_config.h>
#include <private/bionic_defs.h>
#include <private/bionic_malloc_dispatch.h>
@@ -523,6 +524,7 @@
return FreeMallocLeakInfo(reinterpret_cast<android_mallopt_leak_info_t*>(arg));
}
if (opcode == M_SET_HEAP_TAGGING_LEVEL) {
+ ScopedPthreadMutexLocker locker(&g_heap_tagging_lock);
return SetHeapTaggingLevel(arg, arg_size);
}
if (opcode == M_INITIALIZE_GWP_ASAN) {