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Date: Thu, 17 Nov 2022 16:27:42 -0800 From: Kees Cook <keescook@...omium.org> To: Jann Horn <jannh@...gle.com> Cc: Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>, Baolin Wang <baolin.wang@...ux.alibaba.com>, "Jason A. Donenfeld" <Jason@...c4.com>, Eric Biggers <ebiggers@...gle.com>, Huang Ying <ying.huang@...el.com>, Petr Mladek <pmladek@...e.com>, tangmeng <tangmeng@...ontech.com>, "Guilherme G. Piccoli" <gpiccoli@...lia.com>, Tiezhu Yang <yangtiezhu@...ngson.cn>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, linux-doc@...r.kernel.org, Luis Chamberlain <mcgrof@...nel.org>, Seth Jenkins <sethjenkins@...gle.com>, Greg KH <gregkh@...uxfoundation.org>, Linus Torvalds <torvalds@...uxfoundation.org>, Andy Lutomirski <luto@...nel.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, Arnd Bergmann <arnd@...db.de>, Dmitry Vyukov <dvyukov@...gle.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Daniel Bristot de Oliveira <bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>, Andrey Ryabinin <ryabinin.a.a@...il.com>, Alexander Potapenko <glider@...gle.com>, Andrey Konovalov <andreyknvl@...il.com>, Vincenzo Frascino <vincenzo.frascino@....com>, David Gow <davidgow@...gle.com>, "Paul E. McKenney" <paulmck@...nel.org>, Anton Vorontsov <anton@...msg.org>, Mauro Carvalho Chehab <mchehab+huawei@...nel.org>, Laurent Dufour <ldufour@...ux.ibm.com>, Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com, linux-mm@...ck.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH v3 5/6] panic: Introduce warn_limit On Thu, Nov 17, 2022 at 03:43:25PM -0800, Kees Cook wrote: > Like oops_limit, add warn_limit for limiting the number of warnings when > panic_on_warn is not set. > > Cc: Jonathan Corbet <corbet@....net> > Cc: Andrew Morton <akpm@...ux-foundation.org> > Cc: Baolin Wang <baolin.wang@...ux.alibaba.com> > Cc: "Jason A. Donenfeld" <Jason@...c4.com> > Cc: Eric Biggers <ebiggers@...gle.com> > Cc: Huang Ying <ying.huang@...el.com> > Cc: Petr Mladek <pmladek@...e.com> > Cc: tangmeng <tangmeng@...ontech.com> > Cc: "Guilherme G. Piccoli" <gpiccoli@...lia.com> > Cc: Tiezhu Yang <yangtiezhu@...ngson.cn> > Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de> > Cc: linux-doc@...r.kernel.org > Reviewed-by: Luis Chamberlain <mcgrof@...nel.org> > Signed-off-by: Kees Cook <keescook@...omium.org> > --- > Documentation/admin-guide/sysctl/kernel.rst | 9 +++++++++ > kernel/panic.c | 14 ++++++++++++++ > 2 files changed, 23 insertions(+) > > diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst > index 09f3fb2f8585..c385d5319cdf 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -1508,6 +1508,15 @@ entry will default to 2 instead of 0. > 2 Unprivileged calls to ``bpf()`` are disabled > = ============================================================= > > + > +warn_limit > +========== > + > +Number of kernel warnings after which the kernel should panic when > +``panic_on_warn`` is not set. Setting this to 0 or 1 has the same effect > +as setting ``panic_on_warn=1``. > + > + > watchdog > ======== > > diff --git a/kernel/panic.c b/kernel/panic.c > index cfa354322d5f..e5aab27496d7 100644 > --- a/kernel/panic.c > +++ b/kernel/panic.c > @@ -58,6 +58,7 @@ bool crash_kexec_post_notifiers; > int panic_on_warn __read_mostly; > unsigned long panic_on_taint; > bool panic_on_taint_nousertaint = false; > +static unsigned int warn_limit __read_mostly = 10000; > > int panic_timeout = CONFIG_PANIC_TIMEOUT; > EXPORT_SYMBOL_GPL(panic_timeout); > @@ -88,6 +89,13 @@ static struct ctl_table kern_panic_table[] = { > .extra2 = SYSCTL_ONE, > }, > #endif > + { > + .procname = "warn_limit", > + .data = &warn_limit, > + .maxlen = sizeof(warn_limit), > + .mode = 0644, > + .proc_handler = proc_douintvec, > + }, > { } > }; > > @@ -203,8 +211,14 @@ static void panic_print_sys_info(bool console_flush) > > void check_panic_on_warn(const char *origin) > { > + static atomic_t warn_count = ATOMIC_INIT(0); > + > if (panic_on_warn) > panic("%s: panic_on_warn set ...\n", origin); > + > + if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit)) > + panic("%s: system warned too often (kernel.warn_limit is %d)", > + warn_limit); Bah. This should be: origin, warn_limit. -- Kees Cook
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