Re: [PATCH 04/11] kasan: add match-all tag tests

Add 3 new tests for tag-based KASAN modes:

1. Check that match-all pointer tag is not assigned randomly.
2. Check that 0xff works as a match-all pointer tag.
3. Check that there are no match-all memory tags.

Note, that test #3 causes a significant number (255) of KASAN reports
to be printed during execution for the SW_TAGS mode.

Signed-off-by: Andrey Konovalov <redacted>
Link: https://linux-review.googlesource.com/id/I78f1375efafa162b37f3abcb2c5bc2f3955dfd8e
---
 lib/test_kasan.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++
 mm/kasan/kasan.h |  6 ++++
 2 files changed, 99 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 46e578c8e842..f1eda0bcc780 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c

@@ -13,6 +13,7 @@
 #include <linux/mman.h>
 #include <linux/module.h>
 #include <linux/printk.h>
+#include <linux/random.h>
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/uaccess.h>

@@ -790,6 +791,95 @@ static void vmalloc_oob(struct kunit *test)
        vfree(area);
 }

+/*
+ * Check that match-all pointer tag is not assigned randomly for
+ * tag-based modes.
+ */
+static void match_all_not_assigned(struct kunit *test)
+{