eCryptfs: Clear LOOKUP_OPEN flag when creating lower file

eCryptfs was passing the LOOKUP_OPEN flag through to the lower file
system, even though ecryptfs_create() doesn't support the flag. A valid
filp for the lower filesystem could be returned in the nameidata if the
lower file system's create() function supported LOOKUP_OPEN, possibly
resulting in unencrypted writes to the lower file.

However, this is only a potential problem in filesystems (FUSE, NFS,
CIFS, CEPH, 9p) that eCryptfs isn't known to support today.

https://bugs.launchpad.net/ecryptfs/+bug/641703

Reported-by: Kevin Buhr
Cc: stable <stable@kernel.org>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 63e6ec0e8b50..9d1a22d62765 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -71,15 +71,19 @@ ecryptfs_create_underlying_file(struct inode *lower_dir_inode,
         struct vfsmount *lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
         struct dentry *dentry_save;
         struct vfsmount *vfsmount_save;
+        unsigned int flags_save;
         int rc;
 
         dentry_save = nd->path.dentry;
         vfsmount_save = nd->path.mnt;
+        flags_save = nd->flags;
         nd->path.dentry = lower_dentry;
         nd->path.mnt = lower_mnt;
+        nd->flags &= ~LOOKUP_OPEN;
         rc = vfs_create(lower_dir_inode, lower_dentry, mode, nd);
         nd->path.dentry = dentry_save;
         nd->path.mnt = vfsmount_save;
+        nd->flags = flags_save;
         return rc;
 }