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>

1 files changed, 4 insertions, 2 deletions

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;