Kernel-hardening archive on lore.kernel.org
 help / color / Atom feed
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
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();
>  }

  reply index

Thread overview: 12+ 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
2020-01-16  1:23 ` [PATCH v3 6/6] ubsan: Include bug type in report header Kees Cook
2020-01-16 12:32   ` Andrey Konovalov

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CACT4Y+batRaj_PaDnfzLjpLDOCChhpiayKeab-rNLx5LAj1sSQ@mail.gmail.com \
    --to=dvyukov@google.com \
    --cc=akpm@linux-foundation.org \
    --cc=ard.biesheuvel@linaro.org \
    --cc=arnd@arndb.de \
    --cc=aryabinin@virtuozzo.com \
    --cc=dan.carpenter@oracle.com \
    --cc=glider@google.com \
    --cc=gustavo@embeddedor.com \
    --cc=kasan-dev@googlegroups.com \
    --cc=keescook@chromium.org \
    --cc=kernel-hardening@lists.openwall.com \
    --cc=lenaptr@google.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=syzkaller@googlegroups.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Kernel-hardening archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kernel-hardening/0 kernel-hardening/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kernel-hardening kernel-hardening/ https://lore.kernel.org/kernel-hardening \
		kernel-hardening@lists.openwall.com
	public-inbox-index kernel-hardening

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/com.openwall.lists.kernel-hardening


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git