[patch] Null dereference in ext4_ext_migrate()

[Dan Carpenter <error27@gmail.com>]

There is a potential null dereference of tmp_inode.

The patch also removes an unnecessary check for whether tmp_inode is null.

This was found through a code checker (http://repo.or.cz/w/smatch.git/). 
It looks like you might be able to trigger the error by trying to migrate 
a readonly file system.  I have only compile tested though, sorry.

regards,
dan carpenter

Signed-off-by: Dan Carpenter <error27@gmail.com>

--- orig/fs/ext4/migrate.c	2009-01-30 23:55:33.000000000 +0300
+++ devel/fs/ext4/migrate.c	2009-01-30 23:57:14.000000000 +0300
@@ -481,7 +481,7 @@
  					+ 1);
  	if (IS_ERR(handle)) {
  		retval = PTR_ERR(handle);
-		goto err_out;
+		return retval;
  	}
  	tmp_inode = ext4_new_inode(handle,
  				inode->i_sb->s_root->d_inode,
@@ -489,8 +489,7 @@
  	if (IS_ERR(tmp_inode)) {
  		retval = -ENOMEM;
  		ext4_journal_stop(handle);
-		tmp_inode = NULL;
-		goto err_out;
+		return retval;
  	}
  	i_size_write(tmp_inode, i_size_read(inode));
  	/*
@@ -618,8 +617,7 @@

  	ext4_journal_stop(handle);

-	if (tmp_inode)
-		iput(tmp_inode);
+	iput(tmp_inode);

  	return retval;
  }