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From:   Haibo Li <haibo.li@mediatek.com>
To:     <linux-kernel@vger.kernel.org>
CC:     Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        "Andrew Morton" <akpm@linux-foundation.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        <kasan-dev@googlegroups.com>, <linux-mm@kvack.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-mediatek@lists.infradead.org>, <xiaoming.yu@mediatek.com>,
        Haibo Li <haibo.li@mediatek.com>,
        kernel test robot <lkp@intel.com>
Subject: [PATCH] fix comparison of unsigned expression < 0
Date:   Tue, 28 Nov 2023 15:55:32 +0800
Message-ID: <20231128075532.110251-1-haibo.li@mediatek.com>
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Kernel test robot reported:

'''
mm/kasan/report.c:637 kasan_non_canonical_hook() warn:
unsigned 'addr' is never less than zero.
'''
The KASAN_SHADOW_OFFSET is 0 on loongarch64.

To fix it,check the KASAN_SHADOW_OFFSET before do comparison.

Signed-off-by: Haibo Li <haibo.li@mediatek.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/
  202311270743.3oTCwYPd-lkp@intel.com/
---
 mm/kasan/report.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index e77facb62900..dafec2df0268 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -634,10 +634,10 @@ void kasan_non_canonical_hook(unsigned long addr)
 {
 	unsigned long orig_addr;
 	const char *bug_type;
-
+#if KASAN_SHADOW_OFFSET > 0
 	if (addr < KASAN_SHADOW_OFFSET)
 		return;
-
+#endif
 	orig_addr = (addr - KASAN_SHADOW_OFFSET) << KASAN_SHADOW_SCALE_SHIFT;
 	/*
 	 * For faults near the shadow address for NULL, we can be fairly certain
-- 
2.18.0