From 10fb46d5f79147620d0afda7d3d51302a1e38191 Mon Sep 17 00:00:00 2001
From: Mathias Krause <minipli@googlemail.com>
Date: Wed, 3 Jul 2013 15:05:39 -0700
Subject: [PATCH] kprobes: handle empty/invalid input to debugfs "enabled" file

When writing invalid input to 'debug/kprobes/enabled' it'll silently be
ignored.  Even worse, when writing an empty string to this file, the
outcome is purely random as the switch statement will make its decision
based on the value of an uninitialized stack variable.

Fix this by handling invalid/empty input as error returning -EINVAL.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 kernel/kprobes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index bddf3b201a48..6e33498d665c 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2332,6 +2332,7 @@ static ssize_t write_enabled_file_bool(struct file *file,
 	if (copy_from_user(buf, user_buf, buf_size))
 		return -EFAULT;
 
+	buf[buf_size] = '\0';
 	switch (buf[0]) {
 	case 'y':
 	case 'Y':
@@ -2343,6 +2344,8 @@ static ssize_t write_enabled_file_bool(struct file *file,
 	case '0':
 		disarm_all_kprobes();
 		break;
+	default:
+		return -EINVAL;
 	}
 
 	return count;