Patch "kasan/test: avoid gcc warning for intentional overflow" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    kasan/test: avoid gcc warning for intentional overflow

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kasan-test-avoid-gcc-warning-for-intentional-overflo.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 53a37cb948cd0bf77930aa65af70b88b1fc99143
Author: Arnd Bergmann <arnd@xxxxxxxx>
Date:   Mon Feb 12 12:15:52 2024 +0100

    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@xxxxxxxxxx
    Fixes: 3f15801cdc23 ("lib: add kasan test module")
    Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
    Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
    Cc: Alexander Potapenko <glider@xxxxxxxxxx>
    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>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index f0b8b05ccf194..ffedc34714ba7 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -403,7 +403,8 @@ static void kmalloc_oob_16(struct kunit *test)
 	/* 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);