[PATCH v2 6/6] panic: Expose "warn_count" to sysfs

Kees Cook
2022-11-09T20:01:03Z

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@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: tangmeng <tangmeng@uniontech.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@igalia.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Kees Cook <keescook@chromium.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@vger.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@vger.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