Turns out I've actually overintellectualized this test.
I've reworked this patch so that kmalloc_pagealloc_oob_right()
allocates a big chunk of memory from the page allocator (and therefore
is enabled only under CONFIG_SLUB).
kmalloc_large_oob_right() now allocates KMALLOC_MAX_CACHE_SIZE - 256
in both SLAB and SLUB modes.

I'll send the updated patch set later today.

On Tue, Feb 2, 2016 at 5:25 PM, Alexander Potapenko [off-list ref] wrote:

The intention was to detect the situation in which a new allocator
appears for which we don't know how it behaves if we allocate more
than KMALLOC_MAX_CACHE_SIZE.
I agree this makes little sense and we can just stick to
CONFIG_SLAB/CONFIG_SLUB cases.

However I think it's better to keep 'size = KMALLOC_MAX_CACHE_SIZE +
something' to keep this code working in the case the value of
KMALLOC_MAX_CACHE_SIZE changes.

On Tue, Feb 2, 2016 at 4:29 PM, Andrey Ryabinin [off-list ref] wrote:

quoted

On 02/02/2016 08:34 AM, Andrew Morton wrote:

quoted

On Wed, 27 Jan 2016 19:25:06 +0100 Alexander Potapenko [off-list ref] wrote:

quoted

depending on which allocator (SLAB or SLUB) is being used

...

--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c

@@ -68,7 +68,22 @@ static noinline void __init kmalloc_node_oob_right(void)
 static noinline void __init kmalloc_large_oob_right(void)
 {
     char *ptr;
-    size_t size = KMALLOC_MAX_CACHE_SIZE + 10;
+    size_t size;
+
+    if (KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE) {
+            /*
+             * We're using the SLAB allocator. Allocate a chunk that fits
+             * into a slab.
+             */
+            size = KMALLOC_MAX_CACHE_SIZE - 256;
+    } else {
+            /*
+             * KMALLOC_MAX_SIZE > KMALLOC_MAX_CACHE_SIZE.
+             * We're using the SLUB allocator. Allocate a chunk that does
+             * not fit into a slab to trigger the page allocator.
+             */
+            size = KMALLOC_MAX_CACHE_SIZE + 10;
+    }

This seems a weird way of working out whether we're using SLAB or SLUB.

Can't we use, umm, #ifdef CONFIG_SLAB?  If not that then let's cook up
something standardized rather than a weird just-happens-to-work like
this.

Actually it would be simpler to not use KMALLOC_MAX_CACHE_SIZE at all.
Simply replace it with 2 or 3 PAGE_SIZEs.

--
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
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-- 
Alexander Potapenko
Software Engineer

Google Germany GmbH
Erika-Mann-Straße, 33
80636 München

Geschäftsführer: Matthew Scott Sucherman, Paul Terence Manicle
Registergericht und -nummer: Hamburg, HRB 86891
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do not forward it, please inform the sender, and please erase this
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