exit: Expose "oops_count" to sysfs

commit 9db89b41117024f80b38b15954017fb293133364 upstream.

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

Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jann Horn <jannh@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20221117234328.594699-3-keescook@chromium.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/Documentation/ABI/testing/sysfs-kernel-oops_count b/Documentation/ABI/testing/sysfs-kernel-oops_count
new file mode 100644 (file)
index 0000000..156cca9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-oops_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 Oopsed since last boot.

diff --git a/kernel/exit.c b/kernel/exit.c
index 172d7f8..f68a9c6 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -64,6 +64,7 @@
 #include <linux/rcuwait.h>
 #include <linux/compat.h>
 #include <linux/io_uring.h>
+#include <linux/sysfs.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -96,6 +97,25 @@ static __init int kernel_exit_sysctls_init(void)
 late_initcall(kernel_exit_sysctls_init);
 #endif
 
+static atomic_t oops_count = ATOMIC_INIT(0);
+
+#ifdef CONFIG_SYSFS
+static ssize_t oops_count_show(struct kobject *kobj, struct kobj_attribute *attr,
+                              char *page)
+{
+       return sysfs_emit(page, "%d\n", atomic_read(&oops_count));
+}
+
+static struct kobj_attribute oops_count_attr = __ATTR_RO(oops_count);
+
+static __init int kernel_exit_sysfs_init(void)
+{
+       sysfs_add_file_to_group(kernel_kobj, &oops_count_attr.attr, NULL);
+       return 0;
+}
+late_initcall(kernel_exit_sysfs_init);
+#endif
+
 static void __unhash_process(struct task_struct *p, bool group_dead)
 {
        nr_threads--;
@@ -906,8 +926,6 @@ EXPORT_SYMBOL_GPL(do_exit);
 
 void __noreturn make_task_dead(int signr)
 {
-       static atomic_t oops_count = ATOMIC_INIT(0);
-
        /*
         * Take the task off the cpu after something catastrophic has
         * happened.