From: Christoph Lameter Makes SLUB behave like SLAB in this area to avoid issues.... Throw a stack dump to alert people. At some point the behavior should be switched back. NULL is no memory as far as I can tell and if the use asked for 0 bytes then he need to get no memory. Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton --- include/linux/slub_def.h | 8 ++++++-- mm/slub.c | 2 +- 2 files changed, 7 insertions(+), 3 deletions(-) diff -puN include/linux/slub_def.h~slub-allocate-smallest-object-size-if-the-user-asks-for-0-bytes include/linux/slub_def.h --- a/include/linux/slub_def.h~slub-allocate-smallest-object-size-if-the-user-asks-for-0-bytes +++ a/include/linux/slub_def.h @@ -80,8 +80,12 @@ extern struct kmem_cache kmalloc_caches[ */ static inline int kmalloc_index(int size) { - if (size == 0) - return 0; + /* + * We should return 0 if size == 0 but we use the smallest object + * here for SLAB legacy reasons. + */ + WARN_ON(size == 0); + if (size > 64 && size <= 96) return 1; if (size > 128 && size <= 192) diff -puN mm/slub.c~slub-allocate-smallest-object-size-if-the-user-asks-for-0-bytes mm/slub.c --- a/mm/slub.c~slub-allocate-smallest-object-size-if-the-user-asks-for-0-bytes +++ a/mm/slub.c @@ -1979,7 +1979,7 @@ static struct kmem_cache *get_slab(size_ { int index = kmalloc_index(size); - if (!size) + if (!index) return NULL; /* Allocation too large? */ _