linux-hardening - [PATCH 4.14 v2 09/15] exit: Expose "oops

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Message-Id: <20230203003354.85691-10-ebiggers@kernel.org>
Date:   Thu,  2 Feb 2023 16:33:48 -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,
        Arnd Bergmann <arnd@...db.de>,
        Luis Chamberlain <mcgrof@...nel.org>
Subject: [PATCH 4.14 v2 09/15] exit: Expose "oops_count" to sysfs

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

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@...ssion.com>
Cc: Jann Horn <jannh@...gle.com>
Cc: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
Link: https://lore.kernel.org/r/20221117234328.594699-3-keescook@chromium.org
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 .../ABI/testing/sysfs-kernel-oops_count       |  6 +++++
 kernel/exit.c                                 | 22 +++++++++++++++++--
 2 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-oops_count

diff --git a/Documentation/ABI/testing/sysfs-kernel-oops_count b/Documentation/ABI/testing/sysfs-kernel-oops_count
new file mode 100644
index 0000000000000..156cca9dbc960
--- /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@...r.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 482bcaf158127..138b110bf83a1 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -62,6 +62,7 @@
 #include <linux/random.h>
 #include <linux/rcuwait.h>
 #include <linux/compat.h>
+#include <linux/sysfs.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -95,6 +96,25 @@ 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--;
@@ -949,8 +969,6 @@ 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.
-- 
2.39.1