linux-kernel - Re: [PATCH v6 5/5] mm: kasan: Do not panic if both panic_on_warn and kasan

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Date:   Tue, 21 Apr 2020 17:39:28 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     David Gow <davidgow@...gle.com>
Cc:     Patricia Alfonso <trishalfonso@...gle.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        kunit-dev@...glegroups.com,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [PATCH v6 5/5] mm: kasan: Do not panic if both panic_on_warn and
 kasan_multishot set

On Sat, Apr 18, 2020 at 5:19 AM 'David Gow' via kasan-dev
<kasan-dev@...glegroups.com> wrote:
>
> KASAN errors will currently trigger a panic when panic_on_warn is set.
> This renders kasan_multishot useless, as further KASAN errors won't be
> reported if the kernel has already paniced. By making kasan_multishot
> disable this behaviour for KASAN errors, we can still have the benefits
> of panic_on_warn for non-KASAN warnings, yet be able to use
> kasan_multishot.
>
> This is particularly important when running KASAN tests, which need to
> trigger multiple KASAN errors: previously these would panic the system
> if panic_on_warn was set, now they can run (and will panic the system
> should non-KASAN warnings show up).
>
> Signed-off-by: David Gow <davidgow@...gle.com>

Reviewed-by: Andrey Konovalov <andreyknvl@...gle.com>

> ---
>  mm/kasan/report.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 0c206bbf9cb3..79fe23bd4f60 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -94,7 +94,7 @@ static void end_report(unsigned long *flags)
>         pr_err("==================================================================\n");
>         add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
>         spin_unlock_irqrestore(&report_lock, *flags);
> -       if (panic_on_warn) {
> +       if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
>                 /*
>                  * This thread may hit another WARN() in the panic path.
>                  * Resetting this prevents additional WARN() from panicking the
> --
> 2.26.1.301.g55bc3eb7cb9-goog
>
> --
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