lib/test_kasan.c: add roundtrip tests

In several places we need to be able to operate on pointers which have
gone via a roundtrip:

	virt -> {phys,page} -> virt

With KASAN_SW_TAGS, we can't preserve the tag for SLUB objects, and the
{phys,page} -> virt conversion will use KASAN_TAG_KERNEL.

This patch adds tests to ensure that this works as expected, without
false positives which have recently been spotted [1,2] in testing.

[1] https://lore.kernel.org/linux-arm-kernel/20190819114420.2535-1-walter-zh.wu@mediatek.com/
[2] https://lore.kernel.org/linux-arm-kernel/20190819132347.GB9927@lakrids.cambridge.arm.com/

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20190821153927.28630-1-mark.rutland@arm.com
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index b63b367..49cc4d5 100644 (file)
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -18,6 +18,9 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/uaccess.h>
+#include <linux/io.h>
+
+#include <asm/page.h>
 
 /*
  * Note: test functions are marked noinline so that their names appear in
@@ -337,6 +340,42 @@ static noinline void __init kmalloc_uaf2(void)
        kfree(ptr2);
 }
 
+static noinline void __init kfree_via_page(void)
+{
+       char *ptr;
+       size_t size = 8;
+       struct page *page;
+       unsigned long offset;
+
+       pr_info("invalid-free false positive (via page)\n");
+       ptr = kmalloc(size, GFP_KERNEL);
+       if (!ptr) {
+               pr_err("Allocation failed\n");
+               return;
+       }
+
+       page = virt_to_page(ptr);
+       offset = offset_in_page(ptr);
+       kfree(page_address(page) + offset);
+}
+
+static noinline void __init kfree_via_phys(void)
+{
+       char *ptr;
+       size_t size = 8;
+       phys_addr_t phys;
+
+       pr_info("invalid-free false positive (via phys)\n");
+       ptr = kmalloc(size, GFP_KERNEL);
+       if (!ptr) {
+               pr_err("Allocation failed\n");
+               return;
+       }
+
+       phys = virt_to_phys(ptr);
+       kfree(phys_to_virt(phys));
+}
+
 static noinline void __init kmem_cache_oob(void)
 {
        char *p;
@@ -737,6 +776,8 @@ static int __init kmalloc_tests_init(void)
        kmalloc_uaf();
        kmalloc_uaf_memset();
        kmalloc_uaf2();
+       kfree_via_page();
+       kfree_via_phys();
        kmem_cache_oob();
        memcg_accounted_kmem_cache();
        kasan_stack_oob();