linux-kernel - [PATCH v2] kunit: kasan_test: disable fortify string checker on kmalloc_oob

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Message-ID: <20231214164423.6202-1-npache@redhat.com>
Date:   Thu, 14 Dec 2023 09:44:23 -0700
From:   Nico Pache <npache@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        kasan-dev@...glegroups.com
Cc:     akpm@...ux-foundation.org, vincenzo.frascino@....com,
        dvyukov@...gle.com, andreyknvl@...il.com, glider@...gle.com,
        ryabinin.a.a@...il.com
Subject: [PATCH v2] kunit: kasan_test: disable fortify string checker on kmalloc_oob_memset

similar to commit 09c6304e38e4 ("kasan: test: fix compatibility with
FORTIFY_SOURCE") the kernel is panicing in kmalloc_oob_memset_*.

This is due to the `ptr` not being hidden from the optimizer which would
disable the runtime fortify string checker.

kernel BUG at lib/string_helpers.c:1048!
Call Trace:
[<00000000272502e2>] fortify_panic+0x2a/0x30
([<00000000272502de>] fortify_panic+0x26/0x30)
[<001bffff817045c4>] kmalloc_oob_memset_2+0x22c/0x230 [kasan_test]

Hide the `ptr` variable from the optimizer to fix the kernel panic.
Also define a memset_size variable and hide that as well. This cleans up
the code and follows the same convention as other tests.

Signed-off-by: Nico Pache <npache@...hat.com>
---
 mm/kasan/kasan_test.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 8281eb42464b..34515a106ca5 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -493,14 +493,17 @@ static void kmalloc_oob_memset_2(struct kunit *test)
 {
 	char *ptr;
 	size_t size = 128 - KASAN_GRANULE_SIZE;
+	size_t memset_size = 2;
 
 	KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
 
 	ptr = kmalloc(size, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
-	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2));
+	OPTIMIZER_HIDE_VAR(memset_size);
+	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, memset_size));
 	kfree(ptr);
 }
 
@@ -508,14 +511,17 @@ static void kmalloc_oob_memset_4(struct kunit *test)
 {
 	char *ptr;
 	size_t size = 128 - KASAN_GRANULE_SIZE;
+	size_t memset_size = 4;
 
 	KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
 
 	ptr = kmalloc(size, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
-	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4));
+	OPTIMIZER_HIDE_VAR(memset_size);
+	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, memset_size));
 	kfree(ptr);
 }
 
@@ -523,14 +529,17 @@ static void kmalloc_oob_memset_8(struct kunit *test)
 {
 	char *ptr;
 	size_t size = 128 - KASAN_GRANULE_SIZE;
+	size_t memset_size = 8;
 
 	KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
 
 	ptr = kmalloc(size, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
-	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8));
+	OPTIMIZER_HIDE_VAR(memset_size);
+	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, memset_size));
 	kfree(ptr);
 }
 
@@ -538,14 +547,17 @@ static void kmalloc_oob_memset_16(struct kunit *test)
 {
 	char *ptr;
 	size_t size = 128 - KASAN_GRANULE_SIZE;
+	size_t memset_size = 16;
 
 	KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
 
 	ptr = kmalloc(size, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	OPTIMIZER_HIDE_VAR(ptr);
 	OPTIMIZER_HIDE_VAR(size);
-	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16));
+	OPTIMIZER_HIDE_VAR(memset_size);
+	KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, memset_size));
 	kfree(ptr);
 }
 
-- 
2.43.0