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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Thu, 22 Apr 2021 17:06:34 +0200
Message-ID: <CA+fCnZegOsHtWJy2QmVe=y_WHwi5WHFRfHLR6P9SHjX5c-9G7g@mail.gmail.com>
Subject: Re: [PATCH 1/2] mm/kasan: avoid duplicate KASAN issues from reporting
To:     Marco Elver <elver@google.com>,
        Maninder Singh <maninder1.s@samsung.com>
Cc:     Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>, a.sahrawat@samsung.com,
        Vaneet Narang <v.narang@samsung.com>
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On Thu, Apr 22, 2021 at 4:10 PM Marco Elver <elver@google.com> wrote:
>
> On Thu, 22 Apr 2021 at 11:17, Maninder Singh <maninder1.s@samsung.com> wrote:
> >
> > when KASAN multishot is ON and some buggy code hits same code path
> > of KASAN issue repetetively, it can flood logs on console.
> >
> > Check for allocaton, free and backtrace path at time of KASAN error,
> > if these are same then it is duplicate error and avoid these prints
> > from KASAN.
>
> On a more fundamental level, I think this sort of filtering is the
> wrong solution to your problem. One reason why it's good that
> multishot is off by default is, because _every_ KASAN report is
> critical and can destabilize the system. Therefore, any report after
> the first one might be completely bogus, because the system is in a
> potentially bad state and its behaviour might be completely random.
>
> The correct solution is to not leave the system running, fix the first
> bug found, continue; rinse and repeat. Therefore, this patch adds a
> lot of code for little benefit.

I agree with Marco here.

It doesn't make sense to have this deduplication code in the kernel
anyway. If you want unique reports, write a userspace script that
parses dmesg and groups the reports.

Thanks!