[RFC/PATCH 1/3] SLAB: Add PageSlab checking to ksize()

[Pekka J Enberg]

From: Pekka Enberg <penberg@xxxxxxxxxxxxxx>

The ksize() function is meant for objects allocated from the slab caches, not
for arbitrary objects. Add a BUG_ON() to enforce that.

Cc: Christoph Lameter <clameter@xxxxxxx>
Cc: Matt Mackall <mpm@xxxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
---
 mm/slab.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 06236e4..b98bb7c 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -4472,10 +4472,14 @@ const struct seq_operations slabstats_op = {
  */
 size_t ksize(const void *objp)
 {
+	struct page *page;
+
 	BUG_ON(!objp);
 	if (unlikely(objp == ZERO_SIZE_PTR))
 		return 0;
 
-	return obj_size(virt_to_cache(objp));
+	page = virt_to_page(objp);
+	BUG_ON(!PageSlab(page));
+	return obj_size(page_get_cache(page));
 }
 EXPORT_SYMBOL(ksize);
-- 
1.5.2.5

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