eCryptfs: Add getattr function

The i_blocks field of an eCryptfs inode cannot be trusted, but
generic_fillattr() uses it to instantiate the blocks field of a stat()
syscall when a filesystem doesn't implement its own getattr().  Users
have noticed that the output of du is incorrect on newly created files.

This patch creates ecryptfs_getattr() which calls into the lower
filesystem's getattr() so that eCryptfs can use its kstat.blocks value
after calling generic_fillattr().  It is important to note that the
block count includes the eCryptfs metadata stored in the beginning of
the lower file plus any padding used to fill an extent before
encryption.

https://bugs.launchpad.net/ecryptfs/+bug/390833

Reported-by: Dominic Sacré <dominic.sacre@gmx.de>
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 2b449d79b7fa..5726d7adaf5b 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -1006,6 +1006,21 @@ out:
         return rc;
 }
 
+int ecryptfs_getattr(struct vfsmount *mnt, struct dentry *dentry,
+                     struct kstat *stat)
+{
+        struct kstat lower_stat;
+        int rc;
+
+        rc = vfs_getattr(ecryptfs_dentry_to_lower_mnt(dentry),
+                         ecryptfs_dentry_to_lower(dentry), &lower_stat);
+        if (!rc) {
+                generic_fillattr(dentry->d_inode, stat);
+                stat->blocks = lower_stat.blocks;
+        }
+        return rc;
+}
+
 int
 ecryptfs_setxattr(struct dentry *dentry, const char *name, const void *value,
                   size_t size, int flags)
@@ -1135,6 +1150,7 @@ const struct inode_operations ecryptfs_dir_iops = {
 const struct inode_operations ecryptfs_main_iops = {
         .permission = ecryptfs_permission,
         .setattr = ecryptfs_setattr,
+        .getattr = ecryptfs_getattr,
         .setxattr = ecryptfs_setxattr,
         .getxattr = ecryptfs_getxattr,
         .listxattr = ecryptfs_listxattr,