Index: lib/msan/tests/msan_test.cc
===================================================================
--- lib/msan/tests/msan_test.cc
+++ lib/msan/tests/msan_test.cc
@@ -1214,17 +1214,23 @@
 }
 
 TEST(MemorySanitizer, shmat) {
-  void *p = mmap(NULL, 4096, PROT_READ | PROT_WRITE,
+  const int kShmSize = 4096;
+  void *p = mmap(NULL, kShmSize + SHMLBA, PROT_READ | PROT_WRITE,
                  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
   ASSERT_NE(MAP_FAILED, p);
 
+  if ((unsigned long)p % SHMLBA != 0) {
+    *(unsigned long*)&p = ((unsigned long)p + SHMLBA - 1) / SHMLBA * SHMLBA;
+  }
+  // p is now SHMLBA-aligned;
+
   ((char *)p)[10] = *GetPoisoned<U1>();
   ((char *)p)[4095] = *GetPoisoned<U1>();
 
-  int res = munmap(p, 4096);
+  int res = munmap(p, kShmSize);
   ASSERT_EQ(0, res);
 
-  int id = shmget(IPC_PRIVATE, 4096, 0644 | IPC_CREAT);
+  int id = shmget(IPC_PRIVATE, kShmSize, 0644 | IPC_CREAT);
   ASSERT_GT(id, -1);
 
   void *q = shmat(id, p, 0);