ecryptfs: initialize private persistent file before dereferencing pointer

Ecryptfs_open dereferences a pointer to the private lower file (the one
stored in the ecryptfs inode), without checking if the pointer is NULL.
Right afterward, it initializes that pointer if it is NULL.  Swap order of
statements to first initialize.  Bug discovered by Duckjin Kang.

Signed-off-by: Duckjin Kang <fromdj2k@gmail.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Cc: Dustin Kirkland <kirkland@canonical.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index 3efc7fdc3c3963cd2a3108415b314e66ed04cee1..dde7bb48bb5f8a4430a591e7dc5fb45851beb9fc 100644 (file)
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -191,13 +191,6 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
                                      | ECRYPTFS_ENCRYPTED);
        }
        mutex_unlock(&crypt_stat->cs_mutex);
-       if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_RDONLY)
-           && !(file->f_flags & O_RDONLY)) {
-               rc = -EPERM;
-               printk(KERN_WARNING "%s: Lower persistent file is RO; eCryptfs "
-                      "file must hence be opened RO\n", __func__);
-               goto out;
-       }
        if (!ecryptfs_inode_to_private(inode)->lower_file) {
                rc = ecryptfs_init_persistent_file(ecryptfs_dentry);
                if (rc) {
@@ -208,6 +201,13 @@ static int ecryptfs_open(struct inode *inode, struct file *file)
                        goto out;
                }
        }
+       if ((ecryptfs_inode_to_private(inode)->lower_file->f_flags & O_RDONLY)
+           && !(file->f_flags & O_RDONLY)) {
+               rc = -EPERM;
+               printk(KERN_WARNING "%s: Lower persistent file is RO; eCryptfs "
+                      "file must hence be opened RO\n", __func__);
+               goto out;
+       }
        ecryptfs_set_file_lower(
                file, ecryptfs_inode_to_private(inode)->lower_file);
        if (S_ISDIR(ecryptfs_dentry->d_inode->i_mode)) {