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authorLaura Abbott <labbott@fedoraproject.org>2016-02-25 16:36:43 -0800
committerKees Cook <keescook@chromium.org>2016-03-01 14:29:13 -0800
commit250a8988ef4071d8b7cdbb27388f09f33402293a (patch)
tree44943637efcbf5405da8308fd5effe77a4e740de /drivers/misc/lkdtm.c
parentbc0b8cc6cb26a209fa1679d5c063b47bc0afe964 (diff)
downloadlinux-250a8988ef4071d8b7cdbb27388f09f33402293a.tar.gz
lkdtm: Update WRITE_AFTER_FREE test
The SLUB allocator may use the first word of a freed block to store the freelist information. This may make it harder to test poisoning features. Change the WRITE_AFTER_FREE test to better match what the READ_AFTER_FREE test does and also print out a big more information. Signed-off-by: Laura Abbott <labbott@fedoraproject.org> Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'drivers/misc/lkdtm.c')
-rw-r--r--drivers/misc/lkdtm.c17
1 files changed, 13 insertions, 4 deletions
diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
index 8de47462638a..a00a2b11b821 100644
--- a/drivers/misc/lkdtm.c
+++ b/drivers/misc/lkdtm.c
@@ -411,12 +411,21 @@ static void lkdtm_do_action(enum ctype which)
break;
}
case CT_WRITE_AFTER_FREE: {
+ int *base;
size_t len = 1024;
- u32 *data = kmalloc(len, GFP_KERNEL);
+ /*
+ * 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
+ */
+ size_t offset = (len / sizeof(*base)) / 2;
- kfree(data);
- schedule();
- memset(data, 0x78, len);
+ base = kmalloc(len, GFP_KERNEL);
+ pr_info("Allocated memory %p-%p\n", base, &base[offset * 2]);
+ kfree(base);
+ pr_info("Attempting bad write to freed memory at %p\n",
+ &base[offset]);
+ base[offset] = 0x0abcdef0;
break;
}
case CT_READ_AFTER_FREE: {