fs/cifs: make share unaccessible at root level mountable

commit a6b5058fafdf508904bbf16c29b24042cef3c496 upstream.

if, when mounting //HOST/share/sub/dir/foo we can query /sub/dir/foo but
not any of the path components above:

- store the /sub/dir/foo prefix in the cifs super_block info
- in the superblock, set root dentry to the subpath dentry (instead of
  the share root)
- set a flag in the superblock to remember it
- use prefixpath when building path from a dentry

fixes bso#8950

Signed-off-by: Aurelien Aptel <aaptel@suse.com>
Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 18 insertions, 2 deletions

diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
index c3eb998a99bd..b95bffcee8aa 100644
--- a/fs/cifs/dir.c
+++ b/fs/cifs/dir.c
@@ -84,6 +84,7 @@ build_path_from_dentry(struct dentry *direntry)
 	struct dentry *temp;
 	int namelen;
 	int dfsplen;
+	int pplen = 0;
 	char *full_path;
 	char dirsep;
 	struct cifs_sb_info *cifs_sb = CIFS_SB(direntry->d_sb);
@@ -95,8 +96,12 @@ build_path_from_dentry(struct dentry *direntry)
 		dfsplen = strnlen(tcon->treeName, MAX_TREE_SIZE + 1);
 	else
 		dfsplen = 0;
+
+	if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_USE_PREFIX_PATH)
+		pplen = cifs_sb->prepath ? strlen(cifs_sb->prepath) + 1 : 0;
+
 cifs_bp_rename_retry:
-	namelen = dfsplen;
+	namelen = dfsplen + pplen;
 	seq = read_seqbegin(&rename_lock);
 	rcu_read_lock();
 	for (temp = direntry; !IS_ROOT(temp);) {
@@ -137,7 +142,7 @@ cifs_bp_rename_retry:
 		}
 	}
 	rcu_read_unlock();
-	if (namelen != dfsplen || read_seqretry(&rename_lock, seq)) {
+	if (namelen != dfsplen + pplen || read_seqretry(&rename_lock, seq)) {
 		cifs_dbg(FYI, "did not end path lookup where expected. namelen=%ddfsplen=%d\n",
 			 namelen, dfsplen);
 		/* presumably this is only possible if racing with a rename
@@ -153,6 +158,17 @@ cifs_bp_rename_retry:
 	   those safely to '/' if any are found in the middle of the prepath */
 	/* BB test paths to Windows with '/' in the midst of prepath */
 
+	if (pplen) {
+		int i;
+
+		cifs_dbg(FYI, "using cifs_sb prepath <%s>\n", cifs_sb->prepath);
+		memcpy(full_path+dfsplen+1, cifs_sb->prepath, pplen-1);
+		full_path[dfsplen] = '\\';
+		for (i = 0; i < pplen-1; i++)
+			if (full_path[dfsplen+1+i] == '/')
+				full_path[dfsplen+1+i] = CIFS_DIR_SEP(cifs_sb);
+	}
+
 	if (dfsplen) {
 		strncpy(full_path, tcon->treeName, dfsplen);
 		if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) {