[PATCH 05/10] mm: kmemcheck skip object if slab allocation failed

[Jesper Dangaard Brouer <brouer@redhat.com>]

In the SLAB allocator kmemcheck_slab_alloc() is guarded against
being called in case the object is NULL.  In SLUB allocator this
NULL pointer invocation can happen, which seems like an oversight.

Move the NULL pointer check into kmemcheck code (kmemcheck_slab_alloc)
so the check gets moved out of the fastpath, when not compiled
with CONFIG_KMEMCHECK.

This is a step towards sharing post_alloc_hook between SLUB and
SLAB, because slab_post_alloc_hook() does not perform this check
before calling kmemcheck_slab_alloc().

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
---
 mm/kmemcheck.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/kmemcheck.c b/mm/kmemcheck.c
index cab58bb592d8..6f4f424037c0 100644
--- a/mm/kmemcheck.c
+++ b/mm/kmemcheck.c
@@ -60,6 +60,9 @@ void kmemcheck_free_shadow(struct page *page, int order)
 void kmemcheck_slab_alloc(struct kmem_cache *s, gfp_t gfpflags, void *object,
 			  size_t size)
 {
+	if (unlikely(!object)) /* Skip object if allocation failed */
+		return;
+
 	/*
 	 * Has already been memset(), which initializes the shadow for us
 	 * as well.

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