eCryptfs: Check for O_RDONLY lower inodes when opening lower files

If the lower inode is read-only, don't attempt to open the lower file
read/write and don't hand off the open request to the privileged
eCryptfs kthread for opening it read/write.  Instead, only try an
unprivileged, read-only open of the file and give up if that fails.
This patch fixes an oops when eCryptfs is mounted on top of a read-only
mount.

Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Eric Sandeen <esandeen@redhat.com>
Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
Cc: ecryptfs-devel@lists.launchpad.net
Cc: stable <stable@kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 9f0aa9883c28..101fe4c7b1ee 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -129,11 +129,10 @@ int ecryptfs_init_persistent_file(struct dentry *ecryptfs_dentry)
                 lower_dentry = ecryptfs_dentry_to_lower(ecryptfs_dentry);
                 rc = ecryptfs_privileged_open(&inode_info->lower_file,
                                               lower_dentry, lower_mnt, cred);
-                if (rc || IS_ERR(inode_info->lower_file)) {
+                if (rc) {
                         printk(KERN_ERR "Error opening lower persistent file "
                                "for lower_dentry [0x%p] and lower_mnt [0x%p]; "
                                "rc = [%d]\n", lower_dentry, lower_mnt, rc);
-                        rc = PTR_ERR(inode_info->lower_file);
                         inode_info->lower_file = NULL;
                 }
         }