[CIFS] Prevent OOPs when mounting with remote prefixpath.

Fixes OOPs with message 'kernel BUG at fs/cifs/cifs_dfs_ref.c:274!'.
Checks if the prefixpath in an accesible while we are still in cifs_mount
and fails with reporting a error if we can't access the prefixpath

Should fix Samba bugs 6086 and 5861 and kernel bug 12192

Signed-off-by: Igor Mammedov <niallain@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index bcf7b5184664..7342bfb02ae0 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -621,7 +621,7 @@ static const struct inode_operations cifs_ipc_inode_ops = {
         .lookup = cifs_lookup,
 };
 
-static char *build_path_to_root(struct cifs_sb_info *cifs_sb)
+char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb)
 {
         int pplen = cifs_sb->prepathlen;
         int dfsplen;
@@ -678,7 +678,7 @@ struct inode *cifs_iget(struct super_block *sb, unsigned long ino)
                 return inode;
 
         cifs_sb = CIFS_SB(inode->i_sb);
-        full_path = build_path_to_root(cifs_sb);
+        full_path = cifs_build_path_to_root(cifs_sb);
         if (full_path == NULL)
                 return ERR_PTR(-ENOMEM);