linux-kernel - Re: [PATCH] fix comparison of unsigned expression

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 28 Nov 2023 17:22:38 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Haibo Li <haibo.li@...iatek.com>
Cc:     <linux-kernel@...r.kernel.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <xiaoming.yu@...iatek.com>,
        kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] fix comparison of unsigned expression < 0

On Tue, 28 Nov 2023 15:55:32 +0800 Haibo Li <haibo.li@...iatek.com> wrote:

> 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.
> 
> --- 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

We'd rather not add ugly ifdefs for a simple test like this.  If we
replace "<" with "<=", does it fix?  I suspect that's wrong.

But really, some hardwired comparison with an absolute address seems
lazy.  If KASAN_SHADOW_OFFSET is variable on a per-architecture basis
then the expression which checks the validity of an arbitrary address
should also be per-architecture.