diff -aruN a/CFRuntime.c b/CFRuntime.c
--- a/CFRuntime.c	2009-02-19 08:32:54.000000000 -0800
+++ b/CFRuntime.c	2011-08-10 16:32:44.000000000 -0700
@@ -73,11 +73,6 @@
 CF_INLINE size_t malloc_size(void* memblock) {
     return _msize(memblock);
 }
-#elif DEPLOYMENT_TARGET_LINUX
-#include <malloc.h>
-CF_INLINE size_t malloc_size(const void *memblock) {
-    return malloc_usable_size((void *)memblock);
-}
 #endif
 
 extern void __HALT(void);
@@ -264,12 +259,21 @@
     if (NULL == memory) {
 	return NULL;
     }
-#if DEPLOYMENT_TARGET_WINDOWS || DEPLOYMENT_TARGET_LINUX
+#if DEPLOYMENT_TARGET_WINDOWS
     // malloc_size won't work if the memory address has been moved
     // (such as a custom allocator that adds its own metadata
     // (e.g. under/overflow guard data), so don't attempt to call it
     // on the allocation return.
     size_t msize = (usesSystemDefaultAllocator) ? malloc_size(memory) : size;
+#elif DEPLOYMENT_TARGET_LINUX
+    // On Linux, across various architectures and versions of the GNU
+    // C Library, malloc_usable_size has been observed to at times return
+    // incorrect values. Since the introspection value-add it provides to
+    // CoreFoundation seems to be of limited utility, we eliminate it and
+    // simpy use the caller-requested size. In addition, memsetting this
+    // small tail block has also been found to cause heap consistency
+    // problems.
+    size_t msize = size;
 #else
     size_t msize = malloc_size(memory);
 #endif
@@ -1098,6 +1100,7 @@
 	usesSystemDefaultAllocator = (allocator == kCFAllocatorSystemDefault);
 
 	if (__CFZombieLevel & (1 << 0)) {
+#if !DEPLOYMENT_TARGET_LINUX
 	    uint8_t *ptr = (uint8_t *)cf - (usesSystemDefaultAllocator ? 0 : sizeof(CFAllocatorRef));
 	    size_t size = malloc_size(ptr);
 	    uint8_t byte = 0xFC;
@@ -1109,6 +1112,7 @@
 		byte = (__CFZombieLevel >> 8) & 0xFF;
 	    }
 	    memset(ptr, byte, size);
+#endif /* !DEPLOYMENT_TARGET_LINUX */
 	}
 	if (!(__CFZombieLevel & (1 << 4))) {
 	    CFAllocatorDeallocate(allocator, (uint8_t *)cf - (usesSystemDefaultAllocator ? 0 : sizeof(CFAllocatorRef)));