kasan: test: bypass __alloc_size checks

Intentional overflows, as performed by the KASAN tests, are detected at
compile time[1] (instead of only at run-time) with the addition of
__alloc_size.  Fix this by forcing the compiler into not being able to
trust the size used following the kmalloc()s.

[1] https://lore.kernel.org/lkml/20211005184717.65c6d8eb39350395e387b71f@linux-foundation.org

Link: https://lkml.kernel.org/r/20211006181544.1670992-1-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.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 aa8e4225021978b82abe52e85b8be12c435c409b..5475fe396ff75650e2bfe1239bd3653c37bb3195 100644 (file)
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -440,6 +440,7 @@ static void kmalloc_oob_memset_2(struct kunit *test)
        ptr = kmalloc(size, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2));
        kfree(ptr);
 }
@@ -452,6 +453,7 @@ static void kmalloc_oob_memset_4(struct kunit *test)
        ptr = kmalloc(size, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4));
        kfree(ptr);
 }
@@ -464,6 +466,7 @@ static void kmalloc_oob_memset_8(struct kunit *test)
        ptr = kmalloc(size, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8));
        kfree(ptr);
 }
@@ -476,6 +479,7 @@ static void kmalloc_oob_memset_16(struct kunit *test)
        ptr = kmalloc(size, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16));
        kfree(ptr);
 }
@@ -488,6 +492,7 @@ static void kmalloc_oob_in_memset(struct kunit *test)
        ptr = kmalloc(size, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test,
                                memset(ptr, 0, size + KASAN_GRANULE_SIZE));
        kfree(ptr);
@@ -497,7 +502,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
 {
        char *ptr;
        size_t size = 64;
-       volatile size_t invalid_size = -2;
+       size_t invalid_size = -2;
 
        /*
         * Hardware tag-based mode doesn't check memmove for negative size.
@@ -510,6 +515,7 @@ static void kmalloc_memmove_negative_size(struct kunit *test)
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
        memset((char *)ptr, 0, 64);
+       OPTIMIZER_HIDE_VAR(invalid_size);
        KUNIT_EXPECT_KASAN_FAIL(test,
                memmove((char *)ptr, (char *)ptr + 4, invalid_size));
        kfree(ptr);

diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
index 7ebf433edef3bb3a93cf6087af578a5182ff7294..b112cbc835e902357707c906f5095835d7ca6066 100644 (file)
--- a/lib/test_kasan_module.c
+++ b/lib/test_kasan_module.c
@@ -35,6 +35,8 @@ static noinline void __init copy_user_test(void)
                return;
        }
 
+       OPTIMIZER_HIDE_VAR(size);
+
        pr_info("out-of-bounds in copy_from_user()\n");
        unused = copy_from_user(kmem, usermem, size + 1);