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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id u12-20020a170903124c00b00186fd3951f7sm2011902plh.211.2022.11.17.16.27.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Nov 2022 16:27:43 -0800 (PST) Date: Thu, 17 Nov 2022 16:27:42 -0800 From: Kees Cook To: Jann Horn Cc: Jonathan Corbet , Andrew Morton , Baolin Wang , "Jason A. Donenfeld" , Eric Biggers , Huang Ying , Petr Mladek , tangmeng , "Guilherme G. Piccoli" , Tiezhu Yang , Sebastian Andrzej Siewior , linux-doc@vger.kernel.org, Luis Chamberlain , Seth Jenkins , Greg KH , Linus Torvalds , Andy Lutomirski , "Eric W. Biederman" , Arnd Bergmann , Dmitry Vyukov , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Daniel Bristot de Oliveira , Valentin Schneider , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Vincenzo Frascino , David Gow , "Paul E. McKenney" , Anton Vorontsov , Mauro Carvalho Chehab , Laurent Dufour , Rob Herring , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v3 5/6] panic: Introduce warn_limit Message-ID: <202211171627.CFC188B@keescook> References: <20221117233838.give.484-kees@kernel.org> <20221117234328.594699-5-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221117234328.594699-5-keescook@chromium.org> Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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 > Cc: Andrew Morton > Cc: Baolin Wang > Cc: "Jason A. Donenfeld" > Cc: Eric Biggers > Cc: Huang Ying > Cc: Petr Mladek > Cc: tangmeng > Cc: "Guilherme G. Piccoli" > Cc: Tiezhu Yang > Cc: Sebastian Andrzej Siewior > Cc: linux-doc@vger.kernel.org > Reviewed-by: Luis Chamberlain > Signed-off-by: Kees Cook > --- > 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