linux-kernel - [PATCH -next] lib/test_kasan: silence a -Warray-bounds warning

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Date:   Tue, 10 Mar 2020 09:37:49 -0400
From:   Qian Cai <cai@....pw>
To:     akpm@...ux-foundation.org
Cc:     aryabinin@...tuozzo.com, glider@...gle.com, dvyukov@...gle.com,
        kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH -next] lib/test_kasan: silence a -Warray-bounds warning

The commit "kasan: add test for invalid size in memmove" introduced a
compilation warning where it used a negative size on purpose. Silence it
by disabling "array-bounds" checking for this file only for testing
purpose.

In file included from ./include/linux/bitmap.h:9,
                 from ./include/linux/cpumask.h:12,
                 from ./arch/x86/include/asm/cpumask.h:5,
                 from ./arch/x86/include/asm/msr.h:11,
                 from ./arch/x86/include/asm/processor.h:22,
                 from ./arch/x86/include/asm/cpufeature.h:5,
                 from ./arch/x86/include/asm/thread_info.h:53,
                 from ./include/linux/thread_info.h:38,
                 from ./arch/x86/include/asm/preempt.h:7,
                 from ./include/linux/preempt.h:78,
                 from ./include/linux/rcupdate.h:27,
                 from ./include/linux/rculist.h:11,
                 from ./include/linux/pid.h:5,
                 from ./include/linux/sched.h:14,
                 from ./include/linux/uaccess.h:6,
                 from ./arch/x86/include/asm/fpu/xstate.h:5,
                 from ./arch/x86/include/asm/pgtable.h:26,
                 from ./include/linux/kasan.h:15,
                 from lib/test_kasan.c:12:
In function 'memmove',
    inlined from 'kmalloc_memmove_invalid_size' at
lib/test_kasan.c:301:2:
./include/linux/string.h:441:9: warning: '__builtin_memmove' pointer
overflow between offset 0 and size [-2, 9223372036854775807]
[-Warray-bounds]
  return __builtin_memmove(p, q, size);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Qian Cai <cai@....pw>
---
 lib/Makefile | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/Makefile b/lib/Makefile
index ab68a8674360..24d519a0741d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -297,6 +297,8 @@ UBSAN_SANITIZE_ubsan.o := n
 KASAN_SANITIZE_ubsan.o := n
 KCSAN_SANITIZE_ubsan.o := n
 CFLAGS_ubsan.o := $(call cc-option, -fno-stack-protector) $(DISABLE_STACKLEAK_PLUGIN)
+# kmalloc_memmove_invalid_size() does this on purpose.
+CFLAGS_test_kasan.o += $(call cc-disable-warning, array-bounds)
 
 obj-$(CONFIG_SBITMAP) += sbitmap.o
 
-- 
1.8.3.1