From eae5f629062d8be0778cecd5edd7e2628b4e101d Mon Sep 17 00:00:00 2001
From: Shirish Pargaonkar <spargaonkar@suse.com>
Date: Wed, 26 Feb 2014 13:41:08 -0600
Subject: [PATCH] cifs: Allow mounts with restricted intermediate paths
 (try #2)


Allow mounts with intermediate paths without access.

Create an anonymous root dentry for a vfsmount with an inode obtained
via path info if any of the intermediate path entries are not accessible
with EACCES error.

If this dentry becomes accessible via other mounts, splice this
anonymous root dentry (and the subtree under it) at the appropriate
place in that mount.


Reference: Samba bugzilla 6950

Signed-off-by: Shirish Pargaonkar <spargaonkar@suse.com>
---
 fs/cifs/cifsfs.c | 25 +++++++++++++++++++++++--
 fs/cifs/dir.c    | 18 ++++++++++++++----
 fs/cifs/inode.c  |  6 ++++--
 3 files changed, 41 insertions(+), 8 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 849f613..35a7a80 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -584,9 +584,12 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
 	char *full_path = NULL;
 	char *s, *p;
 	char sep;
+	int rc;
+	unsigned int xid;
+	struct inode *rinode = NULL;
+	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
 
-	full_path = cifs_build_path_to_root(vol, cifs_sb,
-					    cifs_sb_master_tcon(cifs_sb));
+	full_path = cifs_build_path_to_root(vol, cifs_sb, tcon);
 	if (full_path == NULL)
 		return ERR_PTR(-ENOMEM);
 
@@ -627,6 +630,24 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
 		dput(dentry);
 		dentry = child;
 	} while (!IS_ERR(dentry));
+	if (IS_ERR(dentry) && (PTR_ERR(dentry) == -EACCES) && *s) {
+		xid = get_xid();
+		if (tcon->unix_ext) {
+			rc = cifs_get_inode_info_unix(&rinode, full_path,
+							sb, xid);
+		} else {
+			rc = cifs_get_inode_info(&rinode, full_path, NULL,
+							sb, xid, NULL);
+		}
+		free_xid(xid);
+
+		if ((rc == 0) && (rinode != NULL)) {
+			dentry = d_obtain_alias(rinode);
+			if (IS_ERR(dentry))
+				iput(rinode);
+		}
+	}
+
 	kfree(full_path);
 	return dentry;
 }
diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index 3db0c5f..7eb8ccc 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -702,6 +702,7 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 	struct cifs_tcon *pTcon;
 	struct inode *newInode = NULL;
 	char *full_path = NULL;
+	struct dentry *ret = NULL;
 
 	xid = get_xid();
 
@@ -748,11 +749,19 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 	}
 
 	if ((rc == 0) && (newInode != NULL)) {
-		d_add(direntry, newInode);
 		/* since paths are not looked up by component - the parent
 		   directories are presumed to be good here */
-		renew_parental_timestamps(direntry);
-
+		ret = d_splice_alias(newInode, direntry);
+		if (!ret)
+			renew_parental_timestamps(direntry);
+		else {
+			if (!IS_ERR(ret)) {
+				renew_parental_timestamps(direntry);
+				dput(ret);
+				goto lookup_out;
+			} else
+				rc = PTR_ERR(ret);
+		}
 	} else if (rc == -ENOENT) {
 		rc = 0;
 		direntry->d_time = jiffies;
@@ -764,12 +773,13 @@ cifs_lookup(struct inode *parent_dir_inode, struct dentry *direntry,
 		/* We special case check for Access Denied - since that
 		is a common return code */
 	}
+	ret = ERR_PTR(rc);
 
 lookup_out:
 	kfree(full_path);
 	cifs_put_tlink(tlink);
 	free_xid(xid);
-	return ERR_PTR(rc);
+	return ret;
 }
 
 static int
diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index aadc2b6..00006ab 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -885,8 +885,10 @@ inode_has_hashed_dentries(struct inode *inode)
 	spin_lock(&inode->i_lock);
 	hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) {
 		if (!d_unhashed(dentry) || IS_ROOT(dentry)) {
-			spin_unlock(&inode->i_lock);
-			return true;
+			if (!(dentry->d_flags & DCACHE_DISCONNECTED)) {
+				spin_unlock(&inode->i_lock);
+				return true;
+			}
 		}
 	}
 	spin_unlock(&inode->i_lock);
-- 
1.8.3.2