lkml.org 
[lkml]   [2020]   [May]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/4] lkdtm/heap: Avoid edge and middle of slabs
Date
Har har, after I moved the slab freelist pointer into the middle of the
slab, now it looks like the contents are getting poisoned. Adjust the
test to avoid the freelist pointer again.

Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/misc/lkdtm/heap.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/lkdtm/heap.c b/drivers/misc/lkdtm/heap.c
index 3c5cec85edce..1323bc16f113 100644
--- a/drivers/misc/lkdtm/heap.c
+++ b/drivers/misc/lkdtm/heap.c
@@ -58,11 +58,12 @@ void lkdtm_READ_AFTER_FREE(void)
int *base, *val, saw;
size_t len = 1024;
/*
- * The slub allocator uses the first word to store the free
- * pointer in some configurations. Use the middle of the
- * allocation to avoid running into the freelist
+ * The slub allocator will use the either the first word or
+ * the middle of the allocation to store the free pointer,
+ * depending on configurations. Store in the second word to
+ * avoid running into the freelist.
*/
- size_t offset = (len / sizeof(*base)) / 2;
+ size_t offset = sizeof(*base);

base = kmalloc(len, GFP_KERNEL);
if (!base) {
--
2.25.1
\
 
 \ /
  Last update: 2020-05-29 22:07    [W:0.129 / U:0.328 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site