eCryptfs: Invalidate dcache entries when lower i_nlink is zero

commit 5556e7e6d30e8e9b5ee51b0e5edd526ee80e5e36 upstream.

Consider eCryptfs dcache entries to be stale when the corresponding
lower inode's i_nlink count is zero. This solves a problem caused by the
lower inode being directly modified, without going through the eCryptfs
mount, leaving stale eCryptfs dentries cached and the eCryptfs inode's
i_nlink count not being cleared.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reported-by: Richard Weinberger <richard@nod.at>
[ luis: backported to 3.16:
  - use dentry->d_inode instead of d_inode(dentry)
  - adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

diff --git a/fs/ecryptfs/dentry.c b/fs/ecryptfs/dentry.c
index 4000f6b3a7504505bb46d3d5ef2946b53e3d5cc9..c7703c056e06296e2433fe5e1faa7878c804d415 100644 (file)
--- a/fs/ecryptfs/dentry.c
+++ b/fs/ecryptfs/dentry.c
@@ -45,20 +45,20 @@
 static int ecryptfs_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
        struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry);
-       int rc;
-
-       if (!(lower_dentry->d_flags & DCACHE_OP_REVALIDATE))
-               return 1;
+       int rc = 1;
 
        if (flags & LOOKUP_RCU)
                return -ECHILD;
 
-       rc = lower_dentry->d_op->d_revalidate(lower_dentry, flags);
+       if (lower_dentry->d_flags & DCACHE_OP_REVALIDATE)
+               rc = lower_dentry->d_op->d_revalidate(lower_dentry, flags);
+
        if (dentry->d_inode) {
-               struct inode *lower_inode =
-                       ecryptfs_inode_to_lower(dentry->d_inode);
+               struct inode *inode = dentry->d_inode;
 
-               fsstack_copy_attr_all(dentry->d_inode, lower_inode);
+               fsstack_copy_attr_all(inode, ecryptfs_inode_to_lower(inode));
+               if (!inode->i_nlink)
+                       return 0;
        }
        return rc;
 }