linux-kernel - [PATCH v2 6/6] panic: Expose "warn

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Message-Id: <20221109200050.3400857-6-keescook@chromium.org>
Date:   Wed,  9 Nov 2022 12:00:49 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>, Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        tangmeng <tangmeng@...ontech.com>,
        "Guilherme G. Piccoli" <gpiccoli@...lia.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        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>,
        Jonathan Corbet <corbet@....net>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Huang Ying <ying.huang@...el.com>,
        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-doc@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH v2 6/6] panic: Expose "warn_count" to sysfs

Since Warn count is now tracked and is a fairly interesting signal, add
the entry /sys/kernel/warn_count to expose it to userspace.

Cc: Petr Mladek <pmladek@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: tangmeng <tangmeng@...ontech.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: Tiezhu Yang <yangtiezhu@...ngson.cn>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 .../ABI/testing/sysfs-kernel-warn_count       |  6 +++++
 MAINTAINERS                                   |  1 +
 kernel/panic.c                                | 22 +++++++++++++++++--
 3 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-warn_count

diff --git a/Documentation/ABI/testing/sysfs-kernel-warn_count b/Documentation/ABI/testing/sysfs-kernel-warn_count
new file mode 100644
index 000000000000..08f083d2fd51
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-warn_count
@@ -0,0 +1,6 @@
+What:		/sys/kernel/oops_count
+Date:		November 2022
+KernelVersion:	6.2.0
+Contact:	Linux Kernel Hardening List <linux-hardening@...r.kernel.org>
+Description:
+		Shows how many times the system has Warned since last boot.
diff --git a/MAINTAINERS b/MAINTAINERS
index 0a1e95a58e54..282cd8a513fd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11107,6 +11107,7 @@ L:	linux-hardening@...r.kernel.org
 S:	Supported
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening
 F:	Documentation/ABI/testing/sysfs-kernel-oops_count
+F:	Documentation/ABI/testing/sysfs-kernel-warn_count
 F:	include/linux/overflow.h
 F:	include/linux/randomize_kstack.h
 F:	mm/usercopy.c
diff --git a/kernel/panic.c b/kernel/panic.c
index b235fa4a6fc8..ddf0f8956d6e 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -32,6 +32,7 @@
 #include <linux/bug.h>
 #include <linux/ratelimit.h>
 #include <linux/debugfs.h>
+#include <linux/sysfs.h>
 #include <trace/events/error_report.h>
 #include <asm/sections.h>
 
@@ -107,6 +108,25 @@ static __init int kernel_panic_sysctls_init(void)
 late_initcall(kernel_panic_sysctls_init);
 #endif
 
+static atomic_t warn_count = ATOMIC_INIT(0);
+
+#ifdef CONFIG_SYSFS
+static ssize_t warn_count_show(struct kobject *kobj, struct kobj_attribute *attr,
+			       char *page)
+{
+	return sysfs_emit(page, "%d\n", atomic_read(&warn_count));
+}
+
+static struct kobj_attribute warn_count_attr = __ATTR_RO(warn_count);
+
+static __init int kernel_panic_sysfs_init(void)
+{
+	sysfs_add_file_to_group(kernel_kobj, &warn_count_attr.attr, NULL);
+	return 0;
+}
+late_initcall(kernel_panic_sysfs_init);
+#endif
+
 static long no_blink(int state)
 {
 	return 0;
@@ -211,8 +231,6 @@ 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);
 
-- 
2.34.1