+ slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch added to -mm tree

+ slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch added to -mm tree

[akpm]

The patch titled
     Subject: slub: choose the right freelist pointer location when  creating small caches
has been added to the -mm tree.  Its filename is
     slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch

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------------------------------------------------------
From: "Lin, Zhenpeng" <zplin@psu.edu>
Subject: slub: choose the right freelist pointer location when  creating small caches

When enabling CONFIG_SLUB_DEBUG and booting with "slub_debug=Z", the
kernel crashes at creating caches if the object size is smaller than
2*sizeof(void*).  The problem is due to the wrong calculation of
freepointer_area.  The freelist pointer can be stored in the middle of
object only if the object size is not smaller than 2*sizeof(void*). 
Otherwise, the freelist pointer will be corrupted by SLUB_RED_ZONE.

Link: https://lkml.kernel.org/r/6746FEEA-FD69-4792-8DDA-C78F5FE7DA02@psu.edu
Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object")
Fixes: 89b83f282d8b ("slub: avoid redzone when choosing freepointer location")
Signed-off-by: Zhenpeng Lin <zplin@psu.edu>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/slub.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/slub.c~slub-choose-the-right-freelist-pointer-location-when-creating-small-caches
+++ a/mm/slub.c
@@ -3752,7 +3752,7 @@ static int calculate_sizes(struct kmem_c
 	 * can't use that portion for writing the freepointer, so
 	 * s->offset must be limited within this for the general case.
 	 */
-	freepointer_area = size;
+	freepointer_area = s->object_size;
 
 #ifdef CONFIG_SLUB_DEBUG
 	/*
@@ -3799,7 +3799,7 @@ static int calculate_sizes(struct kmem_c
 		 */
 		s->offset = size;
 		size += sizeof(void *);
-	} else if (freepointer_area > sizeof(void *)) {
+	} else if (freepointer_area > 2 * sizeof(void *)) {
 		/*
 		 * Store freelist pointer near middle of object to keep
 		 * it away from the edges of the object to avoid small
_

Patches currently in -mm which might be from zplin@psu.edu are

slub-choose-the-right-freelist-pointer-location-when-creating-small-caches.patch