[sanitizer_common] Create max_allocation_size_mb flag.

Summary:
The flag allows the user to specify a maximum allocation size that the
sanitizers will honor.  Any larger allocations will return nullptr or
crash depending on allocator_may_return_null.

Reviewers: kcc, eugenis

Reviewed By: kcc, eugenis

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D69576

1 files changed, 9 insertions, 2 deletions

diff --git a/compiler-rt/lib/msan/msan_allocator.cpp b/compiler-rt/lib/msan/msan_allocator.cpp
index 6aa4e273807..a08c1a00d2e 100644
--- a/compiler-rt/lib/msan/msan_allocator.cpp
+++ b/compiler-rt/lib/msan/msan_allocator.cpp
@@ -115,9 +115,16 @@ static Allocator allocator;
 static AllocatorCache fallback_allocator_cache;
 static StaticSpinMutex fallback_mutex;
 
+static uptr max_malloc_size;
+
 void MsanAllocatorInit() {
   SetAllocatorMayReturnNull(common_flags()->allocator_may_return_null);
   allocator.Init(common_flags()->allocator_release_to_os_interval_ms);
+  if (common_flags()->max_allocation_size_mb)
+    max_malloc_size = Min(common_flags()->max_allocation_size_mb << 20,
+                          kMaxAllowedMallocSize);
+  else
+    max_malloc_size = kMaxAllowedMallocSize;
 }
 
 AllocatorCache *GetAllocatorCache(MsanThreadLocalMallocStorage *ms) {
@@ -132,12 +139,12 @@ void MsanThreadLocalMallocStorage::CommitBack() {
 
 static void *MsanAllocate(StackTrace *stack, uptr size, uptr alignment,
                           bool zeroise) {
-  if (size > kMaxAllowedMallocSize) {
+  if (size > max_malloc_size) {
     if (AllocatorMayReturnNull()) {
       Report("WARNING: MemorySanitizer failed to allocate 0x%zx bytes\n", size);
       return nullptr;
     }
-    ReportAllocationSizeTooBig(size, kMaxAllowedMallocSize, stack);
+    ReportAllocationSizeTooBig(size, max_malloc_size, stack);
   }
   MsanThread *t = GetCurrentThread();
   void *allocated;