debugfs: write_file_bool() - ensure strtobool() operates on valid data

In case, userland writes an empty string to a bool debugfs file, buf[]
will still be uninitialized when being passed to strtobool() making the
outcome of that function purely random.

Fix this by always zero-terminating the buffer.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index ff64bcd5b8fb..63146295153b 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -473,6 +473,7 @@ static ssize_t write_file_bool(struct file *file, const char __user *user_buf,
         if (copy_from_user(buf, user_buf, buf_size))
                 return -EFAULT;
 
+        buf[buf_size] = '\0';
         if (strtobool(buf, &bv) == 0)
                 *val = bv;