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>

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 3fed7f0cbcdfe3d2149dd903e6912628ba58da95..948b597671ddde45dd581f6c6502028633782995 100644 (file)
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2322,6 +2322,7 @@ 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':
@@ -2333,6 +2334,8 @@ static ssize_t write_enabled_file_bool(struct file *file,
        case '0':
                disarm_all_kprobes();
                break;
+       default:
+               return -EINVAL;
        }
 
        return count;