From: Punit Agrawal <punitagrawal@gmail.com>
Date: Tue, 14 Sep 2021 23:38:37 +0900
Subject: kprobes: Do not use local variable when creating debugfs file
Git-commit: 8f7262cd66699a4b02eb7549b35c81b2116aad95
Patch-mainline: v5.16-rc1
References: git-fixes

debugfs_create_file() takes a pointer argument that can be used during
file operation callbacks (accessible via i_private in the inode
structure). An obvious requirement is for the pointer to refer to
valid memory when used.

When creating the debugfs file to dynamically enable / disable
kprobes, a pointer to local variable is passed to
debugfs_create_file(); which will go out of scope when the init
function returns. The reason this hasn't triggered random memory
corruption is because the pointer is not accessed during the debugfs
file callbacks.

Since the enabled state is managed by the kprobes_all_disabled global
variable, the local variable is not needed. Fix the incorrect (and
unnecessary) usage of local variable during debugfs_file_create() by
passing NULL instead.

Link: https://lkml.kernel.org/r/163163031686.489837.4476867635937014973.stgit@devnote2

Fixes: bf8f6e5b3e51 ("Kprobes: The ON/OFF knob thru debugfs")
Signed-off-by: Punit Agrawal <punitagrawal@gmail.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Petr Pavlu <petr.pavlu@suse.com>
---
 kernel/kprobes.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2576,7 +2576,6 @@ static const struct file_operations fops
 static int __init debugfs_kprobe_init(void)
 {
 	struct dentry *dir, *file;
-	unsigned int value = 1;
 
 	dir = debugfs_create_dir("kprobes", NULL);
 	if (!dir)
@@ -2588,7 +2587,7 @@ static int __init debugfs_kprobe_init(vo
 		goto error;
 
 	file = debugfs_create_file("enabled", 0600, dir,
-					&value, &fops_kp);
+					NULL, &fops_kp);
 	if (!file)
 		goto error;