linux-kernel - [PATCH v2 5/6] panic: Introduce warn

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Date:   Wed,  9 Nov 2022 12:00:48 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        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, Greg KH <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        Seth Jenkins <sethjenkins@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Arnd Bergmann <arnd@...db.de>, Marco Elver <elver@...gle.com>,
        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>, Mel Gorman <mgorman@...e.de>,
        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>,
        Luis Chamberlain <mcgrof@...nel.org>,
        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: [PATCH v2 5/6] panic: Introduce warn_limit

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
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 Documentation/admin-guide/sysctl/kernel.rst |  9 +++++++++
 kernel/panic.c                              | 13 +++++++++++++
 2 files changed, 22 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 3afd234767bc..b235fa4a6fc8 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 +211,13 @@ static void panic_print_sys_info(bool console_flush)
 
 void check_panic_on_warn(const char *reason)
 {
+	static atomic_t warn_count = ATOMIC_INIT(0);
+
 	if (panic_on_warn)
 		panic("%s: panic_on_warn set ...\n", reason);
+
+	if (atomic_inc_return(&warn_count) >= READ_ONCE(warn_limit))
+		panic("Warned too often (warn_limit is %d)", warn_limit);
 }
 
 /**
-- 
2.34.1