Patch "panic: Expose "warn_count" to sysfs" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    panic: Expose "warn_count" to sysfs

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     panic-expose-warn_count-to-sysfs.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 78a7f8a709542c419ca2bd5ac180bb82f515ee6d
Author: Kees Cook <keescook@xxxxxxxxxxxx>
Date:   Wed Feb 1 20:42:53 2023 -0800

    panic: Expose "warn_count" to sysfs
    
    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@xxxxxxxx>
    Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Cc: tangmeng <tangmeng@xxxxxxxxxxxxx>
    Cc: "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx>
    Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
    Cc: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
    Reviewed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
    Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20221117234328.594699-6-keescook@xxxxxxxxxxxx
    Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
+Description:
+		Shows how many times the system has Warned since last boot.
diff --git a/kernel/panic.c b/kernel/panic.c
index 8f72305dd501..2c118645e740 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -31,6 +31,7 @@
 #include <linux/bug.h>
 #include <linux/ratelimit.h>
 #include <linux/debugfs.h>
+#include <linux/sysfs.h>
 #include <asm/sections.h>
 
 #define PANIC_TIMER_STEP 100
@@ -81,6 +82,25 @@ 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;
@@ -179,8 +199,6 @@ static void panic_print_sys_info(void)
 
 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);