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References: <1470062715-14077-1-git-send-email-aryabinin@virtuozzo.com>
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 <CAG_fn=WP2VmNNuzp1YMi+vPLaG9B3JH9TD4FfzxVyeZL2AyM_Q@mail.gmail.com> <57A0933F.8000706@virtuozzo.com>
From: Alexander Potapenko <glider@google.com>
Date: Tue, 2 Aug 2016 14:53:50 +0200
Message-ID: <CAG_fn=ViiZ+WnL_c6vMg5-4HFeBjMJfm9RU15XO6uVKet+YD_w@mail.gmail.com>
Subject: Re: [PATCH 6/6] kasan: improve double-free reports.
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Sender: owner-linux-mm@kvack.org
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To: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Dave Jones <davej@codemonkey.org.uk>, Vegard Nossum <vegard.nossum@oracle.com>, Sasha Levin <alexander.levin@verizon.com>, Dmitry Vyukov <dvyukov@google.com>, kasan-dev <kasan-dev@googlegroups.com>, LKML <linux-kernel@vger.kernel.org>, Linux Memory Management List <linux-mm@kvack.org>

On Tue, Aug 2, 2016 at 2:34 PM, Andrey Ryabinin <aryabinin@virtuozzo.com> w=
rote:
>
>
> On 08/02/2016 02:39 PM, Alexander Potapenko wrote:
>
>>> +static void kasan_end_report(unsigned long *flags)
>>> +{
>>> +       pr_err("=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\n");
>>> +       add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>> Don't we want to add the taint as early as possible once we've
>> detected the error?
>
> What for?
> It certainly shouldn't be before dump_stack(), otherwise on the first rep=
ort the kernel will claimed as tainted.
Ah, got it. Fair enough.
>
>>>
>>> +void kasan_report_double_free(struct kmem_cache *cache, void *object,
>>> +                       s8 shadow)
>>> +{
>>> +       unsigned long flags;
>>> +
>>> +       kasan_start_report(&flags);
>>> +       pr_err("BUG: Double free or corrupt pointer\n");
>> How about "Double free or freeing an invalid pointer\n"?
>> I think "corrupt pointer" doesn't exactly reflect where the bug is.
>
> Ok
>



--=20
Alexander Potapenko
Software Engineer

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