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Subject: Re: [PATCH v4 1/2] kasan: detect negative size in memory operation
 function
To:     Walter Wu <walter-zh.wu@mediatek.com>,
        Alexander Potapenko <glider@google.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Matthias Brugger <matthias.bgg@gmail.com>
Cc:     kasan-dev@googlegroups.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        wsd_upstream <wsd_upstream@mediatek.com>,
        linux-mediatek@lists.infradead.org,
        Andrew Morton <akpm@linux-foundation.org>
References: <20191112065302.7015-1-walter-zh.wu@mediatek.com>
From:   Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <b2ba5228-dec0-9acf-49e9-d57f156814ef@virtuozzo.com>
Date:   Fri, 22 Nov 2019 01:20:23 +0300
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On 11/12/19 9:53 AM, Walter Wu wrote:
> KASAN missed detecting size is a negative number in memset(), memcpy(),
> and memmove(), it will cause out-of-bounds bug. So needs to be detected
> by KASAN.
> 
> If size is a negative number, then it has a reason to be defined as
> out-of-bounds bug type.
> Casting negative numbers to size_t would indeed turn up as
> a large size_t and its value will be larger than ULONG_MAX/2,
> so that this can qualify as out-of-bounds.
> 
> KASAN report is shown below:
> 
>  BUG: KASAN: out-of-bounds in kmalloc_memmove_invalid_size+0x70/0xa0
>  Read of size 18446744073709551608 at addr ffffff8069660904 by task cat/72
> 
>  CPU: 2 PID: 72 Comm: cat Not tainted 5.4.0-rc1-next-20191004ajb-00001-gdb8af2f372b2-dirty #1
>  Hardware name: linux,dummy-virt (DT)
>  Call trace:
>   dump_backtrace+0x0/0x288
>   show_stack+0x14/0x20
>   dump_stack+0x10c/0x164
>   print_address_description.isra.9+0x68/0x378
>   __kasan_report+0x164/0x1a0
>   kasan_report+0xc/0x18
>   check_memory_region+0x174/0x1d0
>   memmove+0x34/0x88
>   kmalloc_memmove_invalid_size+0x70/0xa0
> 
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=199341
> 
> Signed-off-by: Walter Wu <walter-zh.wu@mediatek.com>
> Reported-by: Dmitry Vyukov <dvyukov@google.com>
> Suggested-by: Dmitry Vyukov <dvyukov@google.com>
> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: Alexander Potapenko <glider@google.com>
> Reported-by: kernel test robot <lkp@intel.com>
> ---

Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>