Slab allocators: fail if ksize is called with a NULL parameter

A NULL pointer means that the object was not allocated.  One cannot
determine the size of an object that has not been allocated.  Currently we
return 0 but we really should BUG() on attempts to determine the size of
something nonexistent.

krealloc() interprets NULL to mean a zero sized object.  Handle that
separately in krealloc().

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 10 insertions, 5 deletions

diff --git a/mm/slab.c b/mm/slab.c
index 6f6abef83a1a..1b240a3029d6 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4446,7 +4446,8 @@ const struct seq_operations slabstats_op = {
  */
 size_t ksize(const void *objp)
 {
-        if (unlikely(ZERO_OR_NULL_PTR(objp)))
+        BUG_ON(!objp);
+        if (unlikely(objp == ZERO_SIZE_PTR))
                 return 0;
 
         return obj_size(virt_to_cache(objp));
diff --git a/mm/slob.c b/mm/slob.c
index a886e83e17ef..de5d5563a46c 100644
--- a/mm/slob.c
+++ b/mm/slob.c
@@ -484,7 +484,8 @@ size_t ksize(const void *block)
 {
         struct slob_page *sp;
 
-        if (unlikely(ZERO_OR_NULL_PTR(block)))
+        BUG_ON(!block);
+        if (unlikely(block == ZERO_SIZE_PTR))
                 return 0;
 
         sp = (struct slob_page *)virt_to_page(block);
diff --git a/mm/slub.c b/mm/slub.c
index b7d3664fa3a9..d7c044dbd157 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2449,7 +2449,8 @@ size_t ksize(const void *object)
         struct page *page;
         struct kmem_cache *s;
 
-        if (unlikely(ZERO_OR_NULL_PTR(object)))
+        BUG_ON(!object);
+        if (unlikely(object == ZERO_SIZE_PTR))
                 return 0;
 
         page = get_object_page(object);
diff --git a/mm/util.c b/mm/util.c
index bf340d806868..5f64026cbb4d 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -81,14 +81,16 @@ EXPORT_SYMBOL(kmemdup);
 void *krealloc(const void *p, size_t new_size, gfp_t flags)
 {
         void *ret;
-        size_t ks;
+        size_t ks = 0;
 
         if (unlikely(!new_size)) {
                 kfree(p);
                 return ZERO_SIZE_PTR;
         }
 
-        ks = ksize(p);
+        if (p)
+                ks = ksize(p);
+
         if (ks >= new_size)
                 return (void *)p;