The patch titled
Subject: kasan/test: avoid gcc warning for intentional overflow
has been added to the -mm mm-unstable branch. Its filename is
kasan-test-avoid-gcc-warning-for-intentional-overflow.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-test-avoid-gcc-warning-for-intentional-overflow.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Arnd Bergmann <arnd@xxxxxxxx>
Subject: kasan/test: avoid gcc warning for intentional overflow
Date: Mon, 12 Feb 2024 12:15:52 +0100
The out-of-bounds test allocates an object that is three bytes too short
in order to validate the bounds checking. Starting with gcc-14, this
causes a compile-time warning as gcc has grown smart enough to understand
the sizeof() logic:
mm/kasan/kasan_test.c: In function 'kmalloc_oob_16':
mm/kasan/kasan_test.c:443:14: error: allocation of insufficient size '13' for type 'struct <anonymous>' with size '16' [-Werror=alloc-size]
443 | ptr1 = kmalloc(sizeof(*ptr1) - 3, GFP_KERNEL);
| ^
Hide the actual computation behind a RELOC_HIDE() that ensures
the compiler misses the intentional bug.
Link: https://lkml.kernel.org/r/20240212111609.869266-1-arnd@xxxxxxxxxx
Fixes: 3f15801cdc23 ("lib: add kasan test module")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kasan/kasan_test.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/kasan/kasan_test.c~kasan-test-avoid-gcc-warning-for-intentional-overflow
+++ a/mm/kasan/kasan_test.c
@@ -440,7 +440,8 @@ static void kmalloc_oob_16(struct kunit
/* This test is specifically crafted for the generic mode. */
KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_GENERIC);
- ptr1 = kmalloc(sizeof(*ptr1) - 3, GFP_KERNEL);
+ /* RELOC_HIDE to prevent gcc from warning about short alloc */
+ ptr1 = RELOC_HIDE(kmalloc(sizeof(*ptr1) - 3, GFP_KERNEL), 0);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);
ptr2 = kmalloc(sizeof(*ptr2), GFP_KERNEL);
_
Patches currently in -mm which might be from arnd@xxxxxxxx are
mm-damon-dbgfs-implement-deprecation-notice-file-fix.patch
kasan-test-avoid-gcc-warning-for-intentional-overflow.patch
