lkml.org 
[lkml]   [2021]   [Jan]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
Subject[PATCH v2 09/14] kasan: adapt kmalloc_uaf2 test to HW_TAGS mode
From
In the kmalloc_uaf2() test, the pointers to the two allocated memory
blocks might happen to be the same, and the test will fail. With the
software tag-based mode, the probability of the that is 1/254, so it's
hard to observe the failure. For the hardware tag-based mode though,
the probablity is 1/14, which is quite noticable.

Allow up to 16 attempts at generating different tags for the tag-based
modes.

Link: https://linux-review.googlesource.com/id/Ibfa458ef2804ff465d8eb07434a300bf36388d55
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
lib/test_kasan.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 283feda9882a..a1a35d75ee1e 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -382,7 +382,9 @@ static void kmalloc_uaf2(struct kunit *test)
{
char *ptr1, *ptr2;
size_t size = 43;
+ int counter = 0;

+again:
ptr1 = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);

@@ -391,6 +393,15 @@ static void kmalloc_uaf2(struct kunit *test)
ptr2 = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

+ /*
+ * For tag-based KASAN ptr1 and ptr2 tags might happen to be the same.
+ * Allow up to 16 attempts at generating different tags.
+ */
+ if (!IS_ENABLED(CONFIG_KASAN_GENERIC) && ptr1 == ptr2 && counter++ < 16) {
+ kfree(ptr2);
+ goto again;
+ }
+
KUNIT_EXPECT_KASAN_FAIL(test, ptr1[40] = 'x');
KUNIT_EXPECT_PTR_NE(test, ptr1, ptr2);

--
2.30.0.284.gd98b1dd5eaa7-goog
\
 
 \ /
  Last update: 2021-01-13 17:25    [W:0.510 / U:0.332 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site