From: Dmitry Vyukov <dvyukov@google.com>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Elena Petrova <lenaptr@google.com>,
Alexander Potapenko <glider@google.com>,
Dan Carpenter <dan.carpenter@oracle.com>,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
Arnd Bergmann <arnd@arndb.de>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
kernel-hardening@lists.openwall.com,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: [PATCH v3 5/6] kasan: Unset panic_on_warn before calling panic()
Date: Thu, 16 Jan 2020 06:23:01 +0100 [thread overview]
Message-ID: <CACT4Y+batRaj_PaDnfzLjpLDOCChhpiayKeab-rNLx5LAj1sSQ@mail.gmail.com> (raw)
In-Reply-To: <20200116012321.26254-6-keescook@chromium.org>
On Thu, Jan 16, 2020 at 2:24 AM Kees Cook <keescook@chromium.org> wrote:
>
> As done in the full WARN() handler, panic_on_warn needs to be cleared
> before calling panic() to avoid recursive panics.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> mm/kasan/report.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/mm/kasan/report.c b/mm/kasan/report.c
> index 621782100eaa..844554e78893 100644
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -92,8 +92,16 @@ 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) {
> + /*
> + * This thread may hit another WARN() in the panic path.
> + * Resetting this prevents additional WARN() from panicking the
> + * system on this thread. Other threads are blocked by the
> + * panic_mutex in panic().
I don't understand part about other threads.
Other threads are not necessary inside of panic(). And in fact since
we reset panic_on_warn, they will not get there even if they should.
If I am reading this correctly, once one thread prints a warning and
is going to panic, other threads may now print infinite amounts of
warning and proceed past them freely. Why is this the behavior we
want?
> + */
> + panic_on_warn = 0;
> panic("panic_on_warn set ...\n");
> + }
> kasan_enable_current();
> }
next prev parent reply other threads:[~2020-01-16 5:23 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 1:23 [PATCH v3 0/6] ubsan: Split out bounds checker Kees Cook
2020-01-16 1:23 ` [PATCH v3 1/6] ubsan: Add trap instrumentation option Kees Cook
2020-01-16 1:23 ` [PATCH v3 2/6] ubsan: Split "bounds" checker from other options Kees Cook
2020-01-16 1:23 ` [PATCH v3 3/6] lkdtm/bugs: Add arithmetic overflow and array bounds checks Kees Cook
2020-01-16 1:23 ` [PATCH v3 4/6] ubsan: Check panic_on_warn Kees Cook
2020-01-16 1:23 ` [PATCH v3 5/6] kasan: Unset panic_on_warn before calling panic() Kees Cook
2020-01-16 5:23 ` Dmitry Vyukov [this message]
2020-01-16 23:49 ` Kees Cook
2020-01-17 9:54 ` Dmitry Vyukov
2020-01-17 21:20 ` Kees Cook
2020-01-18 9:19 ` Dmitry Vyukov
2020-01-16 1:23 ` [PATCH v3 6/6] ubsan: Include bug type in report header Kees Cook
2020-01-16 12:32 ` Andrey Konovalov
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