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kasan/test: avoid gcc warning for intentional overflow 

[ Upstream commit e10aea105e9ed14b62a11844fec6aaa87c6935a3 ]

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@kernel.org
Fixes: 3f15801cdc ("lib: add kasan test module")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Arnd Bergmann 2024-02-12 12:15:52 +01:00 committed by Greg Kroah-Hartman
parent fe86d01ce7
commit d6e646b860
1 changed files with 2 additions and 1 deletions
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3
mm/kasan/kasan_test.c
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@ -450,7 +450,8 @@ static void kmalloc_oob_16(struct kunit *test)
/* This test is specifically crafted for the generic mode. */ /* This test is specifically crafted for the generic mode. */
KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_GENERIC); 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); KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);
ptr2 = kmalloc(sizeof(*ptr2), GFP_KERNEL); ptr2 = kmalloc(sizeof(*ptr2), GFP_KERNEL);