linux-hardening - [PATCH 4.14 14/16] panic: Expose "warn

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Date:   Wed,  1 Feb 2023 21:44:04 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     stable@...r.kernel.org
Cc:     Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        SeongJae Park <sj@...nel.org>,
        Seth Jenkins <sethjenkins@...gle.com>,
        Jann Horn <jannh@...gle.com>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.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>,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: [PATCH 4.14 14/16] panic: Expose "warn_count" to sysfs

From: Kees Cook <keescook@...omium.org>

commit 8b05aa26336113c4cea25f1c333ee8cd4fc212a6 upstream.

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>
Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
Link: https://lore.kernel.org/r/20221117234328.594699-6-keescook@chromium.org
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 .../ABI/testing/sysfs-kernel-warn_count       |  6 +++++
 kernel/panic.c                                | 22 +++++++++++++++++--
 2 files changed, 26 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 0000000000000..08f083d2fd51b
--- /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/kernel/panic.c b/kernel/panic.c
index bfe6e4c5cd0e7..8f7bf0a8cef1a 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -28,6 +28,7 @@
 #include <linux/console.h>
 #include <linux/bug.h>
 #include <linux/ratelimit.h>
+#include <linux/sysfs.h>
 
 #define PANIC_TIMER_STEP 100
 #define PANIC_BLINK_SPD 18
@@ -68,6 +69,25 @@ 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;
@@ -145,8 +165,6 @@ EXPORT_SYMBOL(nmi_panic);
 
 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);
 
-- 
2.39.1