Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags

On Sun, Jul 07, 2019 at 12:57:32AM +1000, Aleksa Sarai wrote:

@@ -1442,8 +1464,11 @@ static int follow_dotdot_rcu(struct nameidata *nd) struct inode *inode = nd->inode; while (1) {

• if (path_equal(&nd->path, &nd->root))
  

• if (path_equal(&nd->path, &nd->root)) {
  

• 	if (unlikely(nd->flags & LOOKUP_BENEATH))
  

• 		return -EXDEV;
  

@@ -1468,6 +1493,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) return -ECHILD; if (&mparent->mnt == nd->path.mnt) break;

• 	if (unlikely(nd->flags & LOOKUP_XDEV))
  

• 		return -EXDEV;
  /* we know that mountpoint was pinned */
  nd->path.dentry = mountpoint;
  nd->path.mnt = &mparent->mnt;
  

@@ -1482,6 +1509,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) return -ECHILD; if (!mounted) break;

• if (unlikely(nd->flags & LOOKUP_XDEV))
  

• 	return -EXDEV;
  

Are you sure these failure exits in follow_dotdot_rcu() won't give suprious hard errors?

• if (unlikely(nd->flags & LOOKUP_BENEATH)) {

• error = dirfd_path_init(nd);
  

• if (unlikely(error))
  

• 	return ERR_PTR(error);
  

• nd->root = nd->path;
  

• if (!(nd->flags & LOOKUP_RCU))
  

• 	path_get(&nd->root);
  

• } if (*s == '/') { if (likely(!nd->root.mnt)) set_root(nd);

@@ -2350,9 +2400,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags) s = ERR_PTR(error); return s; }

• error = dirfd_path_init(nd);
• if (unlikely(error))

• return ERR_PTR(error);
  

• if (likely(!nd->path.mnt)) {

Is that a weird way of saying "if we hadn't already called dirfd_path_init()"?